We examined the single and interactive effects of an insecticide, an herbicide, and a fertilizer on gray treefrog (Hyla versicolor) tadpoles. Tadpoles were reared in mesocosms from hatching through metamorphosis and were exposed to the presence or absence of as many as three contaminants. Tadpoles did not appear to be more susceptible to single versus multiple contaminants, which may result from positive changes in food resources that compensate for the effects of other contaminants. ?? 2006 SETAC.