The object of the study was to determine whether the composition of the diet of sole Solea solea Linnaeus, 1758 throughout the year is influenced only by the presence and abundance of prey or whether in addition it is influenced by a selection procedure resulting from its energetic and nutritional needs. Feeding habits were established by examining the stomach contents of males and females throughout the year. We recorded the presence or absence of each prey item and identified dominant, occasional and accidental prey. Differences in the seasonal composition of the basic diet were analysed (chisquare). Throughout the year, the diet consisted mainly of crustaceans, except in autumn when polychaetes were the most abundant prey. Significant differences (chisquare) in feeding habits were established between seasons and between sexes in each season. Some of the dominant prey (Ampeliscidae and Callianassidae) live exclusively in estuaries and bays, and occur in highest abundance during winter, the season in which sole enter estuaries to spawn. These prey items were present in higher numbers in the stomach contents of the sole during this period, reflecting the dependence of its diet on prey availability. © 1992 Springer-Verlag.