Gut contents were examined in 20 British species of freshwater gastropods. All showed a wide range of diet, with detritus forming the bulk of the food. Algae rarely formed over 25% of the food ingested, fresh macrophytes were rare, and animal remains were insignificant. Planorbarius corneus grew most on a varied diet, then on a eutrophic detritus, and least on an oligotrophic detritus. Diet preference was shown, in the laboratory, and Elodea canadensis (Canadian Pondweed) was rejected by some species. Some of the smallest pulmonates and the benthic prosobranchs lacked sand grains in the gut. Gyranlus albus was not attracted to an algal food source.