Diet of common dolphins off the Portuguese coast was studied based on the examination of stomach contents of 50 stranded and incidentally caught animals. The relative importance of each prey species was assessed through occurrence, numerical and biomass indices. Common dolphins preyed on a large variety of items but four fish and two cephalopod species appeared to form the basis of their diet. Overall, sardine (Sardina
pilchardus) was the most important prey, as given by all the indices used to measure prey relative importance. Although common dolphins preyed mostly on pelagic species, they seemed able to explore habitats with distinct features and employ various foraging strategies. A comparison between the diet of dolphins of different sex and size groups was not indicative of major differences. Common dolphins incidentally caught in fishing nets had taken a higher proportion of sardines, the target species of the fishery.