The capacity of diatom species to survive gastrointestinal passage through algivorous minnows was examined. In order to determine whether diatom taxa varied in digestibility, live/dead ratios of cells taken from the minnows'' feces were compared with live/dead ratios of cells taken from immersed rocks. With the use of Cluster analyses and Student''s t tests, it was concluded that certain diatom species and genera were more resistant to digestion than others. Diatom species that are readily available to grazers are more resistant to digestion, and vice versa. Diatoms that are less available to grazers are less resistant to digestion. Interspecific variation among diatoms in vulnerability to ingestion and digestion may affect community structure and the functioning of benthic algae.