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The breeding and habits of the Antarctic Tern (Sterna vittata) were studied during a summer at the Snares Islands. Daily records were kept of ten nests situated on cliff ledges and rocks. Egg-laying occurred during two periods; late October/early November and late November. The usual clutch was one egg, but some two-egg clutches were laid. Re-laying probably occurred on one occasion when the first clutch was lost. Both parents incubated, and the incubation period averaged 24 days. The chicks were guarded for two to three days after hatching and were fed by both parents. Chicks fledged between 27 and 32 days after hatching. Adverse weather severely restricted chick growth during the early stages of development and was a major factor in chick mortality.