Twenty-one monthly collections of the Antarctic prosobranch gastropod Laevilacunaria antarctica Martens 1885 were obtained by divers at Signy Island, South Orkney Islands. Animals were contagiously distributed in the depth range 2–12 m below mean low water, with a mean monthly density of 199.0 ± 207.3 (S.D.) m−2. Size frequency distribution was analysed, and at least three year classes identified. There was a prolonged annual recruitment from mid winter to mid summer, and juveniles dominated the population numerically for ten months of the year. Growth was seasonal, with a high rate during the Austral spring and summer, and a reduced rate during winter. A mean biomass of 356.3 mg dry tissue wt · m−2 and a total annual production of 812.2 mg · m−2 were estimated for the second year of study, and a production to biomass ratio of 2.28 obtained.