The original factor structure of the Aberrant Behavior Checklist was cross-validated with an American sample of 470 persons with moderate to profound mental retardation, including nonambulatory individuals. The results of the factor analysis with varimax rotation essentially replicated previous findings, suggesting that the original five factors (Irritability, Lethargy, Stereotypic Behavior, Hyperactivity, and Inappropriate Speech) could be cross-validated by factor loadings of individual items. The original five scales continue to show high internal consistency. These factors are easily interpretable and should continue to provide valuable research and clinical information.