Three subspecies currently recognized:
lehmanni Wetmore 1945
Subspecies lehmanni was described from a single, unsexed specimen collected by (and named after) F.C. Lehmann V. at San Marcos (3000 m), Moscopán, Cauca Department, in southwestern Colombia at the head of Magdalena Valley. Very few specimens and confirmed records of this subspecies exist. In his original description, Wetmore (1945) states that a personal communication from Lehmann includes the existence of a female in the collection of the Museo de Historia, Natural of the Universidad del Cauca (in Popayan) that was collected 8 March 1944, at Tijeras in the same area as the type, but at a slightly lower elevation (2300 m). Since these records, however, there have been no modern records (Hilty 1985).
Overall, lehmanni resembles gigantea, but has even more heavily barred underparts (Fjeldså and Krabbe 1990, Krabbe et al. 1994). In his description of the type, Wetmore (1945) describes lehmanni thus: "Similar to Grallaria gigantea gigantea but barring on the central area of the lower surface definitely heavier; dorsal surface olive brown. Forehead tawny basally, with tips of olive-brown, becoming olive brown that extends back over pileum past posterior angle of eyes; back of pileum and upper hindneck rather dull neutral gray; lower hindneck, back, wings and tail olive brown; part of wing coverts, and a few feathers on lower back tipped with tawny and barred subterminally with dull black; upper tail coverts tipped also with tawny, with subterminal barring dark to deep neutral gray; primaries edged narrowly externally with cinnamon-brown, this changing on the outermost to a narrow outer margin of ochraceous-tawny; lores tawny; rictal bristles black; sides of head and neck tawny, barred with dull black; center of throat and upper foreneck ivory yellow, barred with black; chin, foreneck (except for ivory yellow area), upper breast, sides and flanks ochraceous-tawny, heavily barred with black; center of breast and abdomen light ochraceous buff heavily barred with black; under tail coverts ochraceous-tawny without bars or spots; under wing coverts tawny to ochraceous-tawny heavily barred and spotted with black. Maxilla dusky neutral gray; mandible benzo brown; tarsus benzo brown; toes fuscous (from dried skin)." Wetmore (1945) further compares the type specimen of lehmanni with hylodroma: "From Grallaria g. hylodroma the type of this race differs in being decidedly less rufescent on the lower surface, with the dark bars much heavier, these being heavy and distinct on the flanks where they are weak or absent in the west Ecuadorian birds. The under wing coverts are heavily barred and spotted with black as in typical gigantea. The series of hylodroma is so uniform in maintaining these differences that I do not hesitate to describe lehmanni, even though only a single specimen is available. In one way G. g. lehmanni seems to indicate variation or change in coloration in the direction of Grallaria excelsa excelsa Berlepsch from the Merida region in western Venezuela. The two species gigantea and excelsa are similar in bulk and in length of wing, excelsa differing in having the bill, tarsus and foot much more slender. These differences to date are definite but it is possible that the two may intergrade in the intervening area from which no antpitta of this style is yet known".
hylodroma Wetmore, 1945
Subspecies hylodroma was described from Gualea (2000 m), Pichincha Province, northwestern Ecuador. Its known distribution extends from Nariño Department (de Soye et al. 1997) in southwestern Colombia southward on the Pacific slope of Andes to Cotopaxi Province, Ecuador.
Wetmore’s (1945) description of the type: "Similar to Grallaria gigantea gigantea Lawrence, but much more deeply rufescent below, barring on the lower surface less heavy, being especially reduced, in some nearly absent, on the flanks; more olive above on back, wings, and tail; forehead and loral area much brighter, more rufescent; primaries and secondaries margined heavily with russet. Forehead and loral area between tawny and russet; crown and hindneck deep mouse gray, washed anteriorly with bone brown; feathers above and behind eye narrowly barred with russet, forming part of an indistinct ring; rest of dorsal surface olive brown; wing coverts with a slight margin of russet, the inner greater coverts with a narrow subterminal bar of dull black and a narrow tip of russet; outer webs of primaries russet, merging to tawny on the free margin; outer webs of secondaries with a narrow margin of tawny; back, scapulars and rump with a few feathers tipped with russet crossbarred narrowly with one or two narrow bands of dull black; rectrices very narrowly tipped with russet; sides of head, sides of neck, upper breast, sides and flanks amber brown, becoming tawny on the throat, middle of the breast, abdomen and under tail coverts, the whole narrowly barred with sooty black, the barring heaviest on breast, becoming almost obsolete on flanks; center of throat of warm buff, the anterior feathers white basally, the whole forming an indistinct longitudinal line; chin russet; under wing coverts russet, with a few small scattered spots of sooty black. Maxilla natal brown, becoming fuscous black on culmen; mandible honey yellow; tarsus and toes benzo brown (from dried skin)". Wetmore (1945) goes on to add: "The six specimens of this bird examined are so uniform in their differences from the type of gigantea as to leave no question concerning their distinctness in the characters outlined above. Except as noted under Grallaria gigantea gigantea published records of the Giant Antpitta appear to pertain mainly to the present subspecies. Menegaux  listed a male taken by Dr. Rivet at Pachijal on the western slope, his excellent plate showing a bird that agrees in every way with the series here under discussion. Dubois  records the species only from 'Ecuador,' his plate supposedly being taken from the specimen in the Museum in Brussels, which, according to Sclater  was the second one known. Dubois' figure [ ] agrees with hylodroma in the deep rufescent color of the ventral surface, but differs from any specimen seen in the restriction of the black barring on the under surface".
gigantea Lawrence 1866
The type specimen of the nominate race bears only "Ecuador" as the locality. Wetmore (1945), however, with respect to the collection locality of the type, notes: "The specimen that served as Lawrence's type, U. S. Nat. Mus. No. 35,101, came to Baird with a small lot of skins from John Akhurst, a dealer in natural history material of Brooklyn with a letter dated November 25, 1864. It has only Ecuador as a locality and no other data. However, it seems probable that it came from the eastern slope of the Andes as the other skins received with it include Gymnoderus foetidus [Bare-necked Fruitcrow] and Archiplanus leucoramphus leucoramphus [Mountain Caique Cacicus chrysonotus leucoramphus], species found on the eastern slope that have not yet been recorded from western Ecuador". Subspecies gigantea is, so far as known, endemic to the eastern slope of the Ecuadorian Andes, from eastern Carchi and Napo southward to Volcán Tungurahua.
Nominate gigantea is larger than hylodroma and differs by being barred instead of spotted on the under-wing coverts and flanks. It is also paler overall underneath (Krabbe et al. 1994). Lawrence’s (1866) original description of the type is as follows: “Hind part of crown and hind neck dark plumbeous, entire upper plumage besides rich olivaceous brown, front next the bill tinged with rufous; lores, sides of the head and under plumage dark rufous, the middle of the abdomen only paler, the sides of the neck and the whole of the under surface closely banded with black, the under tail coverts are also dark rufous, without bands but marked with a few minute black spots; tail dark chocolate brown; quills blackish-brown with olive brown margins; under wing coverts rufous banded with black; upper mandible black, the under brownish horn color, lighter underneath and at the base; tarsi and toes dark fleshy brown.” Wetmore (1945) further describes the type specimen as “Below paler, the center of the breast and the abdomen being much lighter, becoming ivory yellow along the median line; above browner, back, wings and tail being bister; forehead and loral space duller brown; brown area of pileum more definitely delimited posteriorly, and extending farther back past middle; under wing coverts heavily barred and spotted with fuscous; flanks much more heavily barred.”