Teachers use both positive and negative consequences to influence classroom behaviors. Four experiments were conducted to examine the differential affects of these two types of consequences on the maintenance of appropriate behaviors of hyperactive children. Results of Experiment 1 showed that the use of both positive and negative consequences (combined) was associated with high levels of on-task behaviors. Withdrawal of negative consequences caused a significant and dramatic decrease in on-task performance. The withdrawal of positive consequences produced no change in the rate of on-task behaviors. In Experiments 2, 3, and 4, the on-task results of Experiment 1 were replicated using a different teacher, different children, a counterbalanced design, longer phases, and different types of negative consequences. The withdrawal of negative consequences led to decreases in productivity in Experiment 2. The results of Experiment 3 also suggested that a prudent (e.g., calm, concrete, and consistent) approach to discipline was more effective than an imprudent (e.g., loud, emotional, and inconsistent) approach. Some level of mild negative consequences for inappropriate behavior is an important ingredient in effective classroom management, and qualitatively different negative consequences may have drastically different effects on the behavior of hyperactive students.