The age/length relationship in Baltic flounder (Platichthys flesus) was investigated by sex, based on otolith readings of 2925 individuals sampled from 11 stations along a transect from the Mecklenburg Eight to the Gulf of Finland in autumn 1994. A significant decrease in length at age was observed from the southwestern to the northeastern areas. However, with advancing age the differences in length became less pronounced. The size differences between sexes increased markedly with advancing age. (C) 1999 International Council for the Exploration of the Sea.