The main and side effects of extinction were evaluated in a multiple baseline design across the problem behaviors of two elementary school boys. For each subject, functional analysis procedures resulted in the occurrence and assessment of only one of several problem behaviors reported by teachers. Extinction treatment based on functional analysis outcomes was then applied to the assessed topography and resulted in the emergence of other inappropriate response forms. Each successive behavior was exposed to extinction and changes in previous and subsequent response forms were observed. Both main effects and indirect effects of extinction were examined. Findings are discussed regarding the covariation of responses and implications for the treatment of behavior disorders in applied settings.