We report the first detailed study of the terrestrial invertebrate fauna of the Byers Peninsula SSSI, Livingston Island, South Shetland Islands. Fourteen micro-arthropod taxa (10 Acari, four Collembola) and two Diptera are recorded, including the first record of the mite Edwardzetes dentifer from the maritime Antarctic. The first record of the midge Belgica antarctica from neighbouring Snow Island is also given. Population composition and density were described in samples from a wide range of terrestrial and freshwater habitats. There was no strong relationship between habitat and microarthropod species occurrence, although comparison of completely vegetated and more stony sites revealed greater population densities at the vegetated sites, and different species proportions at each. Some individual samples contained a wide range of species with none achieving numerical dominance, whilst others from superficially similar sites were dominated by one species. Dipterans were limited to a small number of lakes, streams and seepage areas, where they were sometimes abundant. Population density data and species occurrence are compared with previously published studies from the maritime Antarctic and elsewhere.