Abstract Amphibian metamorphosis is a period of drastic morphologic reorganization, during which larvae experience a decrease in locomotor ability and are more vulnerable to predation. Our results indicate that exposure to sublethal concentrations of nitrite in the water induces behavioral and morphologic changes in the Cascades frog (Rana cascadae). Tadpoles exposed to a nitrite concentration of N-NO2- at 3.5 mg/L transformed more slowly than control tadpoles exposed to dechlorinated tap water. No difference 2 was found in time at emergence and snout—vent length at emergence between experimental and control tadpoles, but development was retarded in tadpoles exposed to nitrite and they emerged at an earlier developmental stage. Also, tadpoles exposed to nitrite occupied shallow water more frequently than did control tadpoles.