Contaminant-induced feeding pattern changes may be a consequence or cause of changes in internal energy stores. Juvenile fathead minnows (Pimephalespromelas; 25 ? 3 mm standard length) were exposed to O.O., 0.5 or 1.0 ppm lead (Pb) during a 2-week preexposure and 2-week testing period (4 weeks total exposure). Changes in prey size selectivity, satiation levels, defecation rates, and weight were recorded. When simultaneously offered two prey sizes (10 2-day-old and 10 7-dayold Daphnia magna) control fish began switching from larger, more difficult-to-capture 7-day-old daphnids to smaller, easier-to-catch 2-day-old prey [analysis of variance (ANOVA) p < 0.061 by day 3. Fish exposed to 0.5 ppm Pb displayed a significant switching (ANOVA, p < 0.06) by day 10. Fish exposed to 1 .O ppm Pb did not significantly change their preference for 7-day-old daphnids. After 2 weeks of Pb exposure, control fish ate more flake food and did not satiate as quickly as exposed groups (ANOVA, p < 0.05). Fish exposed to 1.0 ppm Pb displayed reductions in amount of food remaining by day 4; control and 0.5 ppm Pb-exposed fish displayed a steady decline in the amount of food remaining. Daily defecation rates of Pb-exposed fish were significantly higher than controls (ANOVA, p < 0.05). Although all groups gained weight, there was a significantly smaller increase in Pb-exposed groups (ANOVA, p < 0.05). By altering prey size choices and rate of switching to energetically less costly prey, increasing perseveration (i.e,, repeated efforts to capture single prey item) and visuoipsychomotor difficulty, shortening feeding bouts, and increasing defecation rates, Pb may cause metabolic imbalances in juvenile fish.