Summary - Populations of three species of nematodes, Pelodera arnbomi n. sp., Plectus rhizophilus and Acrobeloides nanus, are described from the Subantarctic island South Georgia for the first rime. Pelodera arnbomi n. sp. differs from ail species of Pelodera with a dome-shaped female tail by its conical female tail shape. Ir differs from P. teres, P. conica and P. incilal1à by the number of preanal papillae in the male bursa (2 vs> 2). It is distinguished from P. punclala by a smaller body size (880 f.Lm vs 1200-2500 f.Lm) and smaller c' -value (2.8 vs 4) and from P. comaruiol1'ca by a smaller body size (880 vs 1080-1500 f.Lm) and larger c'-value (2.8 vs 1.5) in the females. The relation between sorne species of Plectus, especially the identiry of P. rhizophilus and P. varians, is discussed. A population of A. nanus from East Falkland Island is compared with the South Georgia population and found to differ significantly in many quantitative characters. However, the ranges of measurements and ratios and also the qualitative characters are overlapping bet\veen the two populations.