This study investigated the use of an unsignalled continuous avoidance technique to evaluate the subacute effects of 2,4-dichlorophenoxyacetic acid (2,4-D amine) on conditioned avoidance learning in goldfish. Goldfish were exposed to 20 ppm of 2,4-D for either 24 h or 2 weeks at different times during conditioning. The results indicate no significant differences between the controls and the fish exposed for 24 h on the ninth day of conditioning. However, fish treated for 24 h on the first day of conditioning exhibited differences in the magnitude of avoidance responding. In addition, fish exposed for 2 weeks showed significant differences in the pattern, rate of acquisition, and maintenance of the avoidance baseline. Behavioral differences also persisted during a postexposure period in the fish exposed for 2 weeks. This study illustrates the sensitivity of the unsignalled avoidance technique in evaluating conditioned avoidance behavior of fish.