A withdrawal design repeated across three children enrolled in two Head Start classrooms was used to investigate the effectiveness of functional assessment-based interventions to decrease inappropriate behavior. The two questions addressed in the study were (a) Will a behavior intervention plan based on functional behavior assessment conducted in the natural setting be effective in reducing inappropriate classroom behavior for young children? and (b) Will teachers perceive assessment-based interventions to be acceptable and feasible? Results indicated that the procedure yielded effective behavior interventions and teachers found the interventions socially valid. The use of functional assessment as a preventive and proactive strategy is discussed. (Contains 4 tables and 4 figures.)