Individuals with Pervasive Developmental Disorders (PDD) have social competence impairments that can result in negative adult outcomes. Despite considerable research on social skills training, little is available to evaluate these programs. This study describes the development, administration, and utility of a progress-monitoring tool for assessing social skill constructs. The General Social Outcome Measure (GSOM) was developed to capture change in social competence abilities. The GSOM assessed students before, during, and after a scaffolded five-unit social competence intervention (SCI) for youth (ages 10-15 years) with PDD. Repeated measures ANOVAs on GSOM scores (N = 42) revealed significant changes. This study provides initial direction for the design and use of performance-based assessments, such as the GSOM, for effective decision making in the evaluation of SCIs. (Contains 3 tables and 1 figure.)