Six new nematode species of two genera are described from mosses on Signy Island, South Orkney Islands in the maritime Antarctic. Teratocephalus tilbrooki n. sp. is nearest to T. brevicaudatus, T. lirellus and T. deconincki but is characterised by relatively smaller post-labial cervical expansion, relatively longer post-vulval sac, body size, metarhabdion length, angle of inclination of cephalic plicae, anastomosing body annules, absence of longitudinal body ridges, common occurrence of males and greater spicule length. T. rugosus n. sp. is closest to T. subvexus, T. lirellus, T. dadayi and T. tilbrooki n. sp. but differs in body length, length of post-vulval sac and metarhabdions, presence of thirteen to seventeen longitudinal body ridges, anastomosis of some body annules, lateral fields with two crenate incisures, minutely bifurcate tail terminus, common occurrence of males and positions of anterior and posterior subventral genital papillae in males. T. pseudolirellus n. sp. is close to T. lirellus and T. terrestris but is characterised by small metarhabdions, 18-21 faint longitudinal body ridges, minutely bifurcate tail terminus, body size, very short post-vulval sac, anastomosis of some body annules, origin and termination of lateral fields, ratio of T/ABW and absence of males. Aphelenchoides vaughani n. sp. is nearest to A. cyrtus, A. echinocaudatus, A. saprophilus, A. singhi, A. spaskii and A. haguei n. sp. but is distinguished by short body length, shape of mucron, short stylet with basal swellings, short post-vulval sac, shape of lips and absence of males. A. haguei n. sp. is closest to A. arcticus, A. cyrtus, A. echinocaudatus, A. lilium, A. lucknowensis, A. saprophilus, A. singhi, A. spaskii, A. submersus and A. tumulicaudatus but is differentiated by body size, shape of mucron, length of post-vulval sac, more anterior vulva, length of stylet which has basal swellings, shape of lips, position of excretory pore, common occurrence of males and size and shape of spicules. A. helicosoma n. sp. is nearest to A. parietinus, A. fluviatilis, A. rarus and A. seiachicus but is distinguished by the characteristic curled body shape when heat killed, body size, length of basally swollen stylet, short post-vulval sac, high, round lip region, two incisures in lateral fields, position of excretory pore, hemizonid and hemizonion, common occurrence of males, expanded cloacal region, shape and size of spicules, and reflexed testis.