Body composition was measured in male American kestrels (Falco sparverius) beginning after a 77-day exposure to 0, 6, or 12 ppm (dry wt.) selenium as seleno-L-methionine in their diet. Total body mass, lean body mass, and body fat were compared among groups to identify potential wasting effects of selenium, as had been reported for wild waterfowl from a selenium-contaminated site. On the last day of selenium treatment, selenium concentrations in the blood of kestrels was significantly negatively correlated with lean mass. Kestrels that had been exposed to 12 ppm selenium in the diet exhibited relatively higher lean mass (relative to total body mass) and lower normalized body fat than kestrels fed 0 or 6 ppm dietary selenium. These differences persisted throughout the 6 mo study period. The effect observed on body condition of kestrels at environmentally relevant exposure levels has implications for wild birds with respect to both overwinter survival and reproductive success.