Ozone (O3), a reactive component of air pollution, depresses feeding and voluntary locomotor behavior in laboratory rodents, but the effects of O3 on amphibian behavior are not known. We evaluated the effects of 4 h of exposure to air or ozone (0.6 microl/L), on two ecologically relevant behaviors of the toad Bufo marinus. Toads were offered five mealworms at 1, 24, and 48 h after exposure. One hour after exposure, O3-exposed toads ate fewer mealworms than did air-exposed toads (Fisher exact test, p=0.005). Within 24 h after exposure, all toads ate four or five mealworms. Because movement is a key component of toad feeding behavior, we tested additional toads (n=25) for voluntary locomotor behavior during three 1-h trials in a 2.9-m2 open-field arena. Mean (+/-standard deviation) total distance moved was: pre-exposure, 29+/-19.5 m; 1-h postexposure, 13+/-15.6 m; and 24-h postexposure, 17+/-17.4 m. The means were not statistically different by repeated measures analysis of covariance. Therefore, our results suggest that a single 4-h exposure to O3 depresses toad feeding behavior after exposure but had little effect on voluntary locomotor behavior.