Mycosporine-like amino acids (MAAs) that absorb UV radiation (310-360 nm) were investigated in 34 species of benthic marine invertebrates (fourteen sponges, two cnidarians, one nemertean, four molluscs, one bryozoan, two arthropods, eight echinoderms and two tunicates), two species of benthic fish and two species of red algae collected during the spring of 1992 from McMurdo Sound. In addition, MAAs were measured in the ripe ovaries, testes and brooded juveniles of four species of echinoderms. While 90% of the: species had MAAs in their tissues, both quantitative and qualitative measurements reflected a general lack of UV protectants among these fauna. Eight MAAs were detected among the species examined, but only four of these (mycosporine-glycine, shinorine, porphyra-334 and palythine) occurred in any appreciable number: of the species. Palythinol only occurred in the sponge Isodictya erinacea and asterina-330 and palythene only occurred in the red alga Iridaea cordata. MAAs were detected in the ripe ovaries and testes of the sea urchin Sterechinus neumayeri and the ripe varies and brooded young of the sea cucumber Cucumaria ferrari. Low levels and abundances of MAAs may reflect a reduced need for UV protectants in marine organisms inhabiting subtidal (>20 m depth) benthic environments that experience seasonal sea-ice cover. Low concentrations of MAAs may also be a function of diet, since the majority of benthic species present in McMurdo Sound are not herbivorous.