Data from several summer surveys to the Antarctic Peninsula region were analysed to calculate length and age at maturity for the Antarctic krill Euphausia superba. L50 values of 34.62 to 35.90 mm for female krill are the best estimates for the high spawning season. Males attain sexual maturity later at a length between L50 = 43.33 and 43.79 mm. Length at maturity, and length at first spawning are identical for krill. Comparisons with length at age data show that females mature in the third year of the life cycle (age class 2 +), while males reach maturity in the fourth year as age class 3 +. Both sexes show knife-edge maturity.