The side effects of reinforcing compliance to "do" and "don't" requests were examined in this scudy. The study was designed to do two things: (1) further establish that "do" and "don't" requests are functionally distinct and (2) determine which "don't" requests will show the same ability as "do" requests in effecting a change in topographically different inappropriate behaviors. Three children (2 boys and 1 girl), ages 5 yr. 2 mo. to 6 yr. 7 mo., participated. The design of the study was ABAC counterbalanced across subjects. With all three children reinforcement of "do" requests led to increased compliance with "do" requests without concurrent increase in compliance to "don't" requests. Also, reinforcing compliance to "don't" requests resulted in increased compliance to "don't" requests without concurrent increase in compliance to "do" requests. An undesirable side effect to the treatment was also noted. Two children showed a tendency to increase their rates of inappropriate behavior concurrent with increases in compliance to "don't" requests. Probable causes for this effect and concerns about the reinforcement of "don't" requests were discussed.