Two eastern Pennsylvania populations of the cutlips minnow,Exoglossum maxillingua, were studied; one from the Delaware River drainage and the other from the Susquehanna. Specimens were collected by electroshocker during July 1979. Gut content analysis revealed that the cutlips minnow diet varied with age. Major food items included larval trichopterans, especially hydropsychids, and also chironomidlarvae. Cutlips minnows did not exhibit obvious sexual dimorphism outside of their spawning season. Sex ratios tended to emphasize females, presumably related to higher spawning-related mortality among males. Scale analysis and length-frequency showed that individuals ranged up to IV+ years of age, with I+ and II+ age classes predominating. No significant differences between the length-weight relationships of the two populations were evident.