Discriminant analysis of eight morphometric measurements was used to determine the sex of Adélie penguins. A sample of 46 adult birds was taken for measurement from the breeding population at Stranger Point (King George/25 de Mayo Is., South Shetland Islands). The sex of each bird had been determined earlier by means of observing the birds' breeding behaviour (first incubation shift). It was found that the combination of flipper breadth, bill depth and length of the middle toe gave the most accurate sex discrimination (87% correct). Using measurements of flipper breadth and bill depth only also gave good results (80% correct).