The Preschool and Kindergarten Behavior Scales (RKBS) was developed to address the lack of psychometrically sound behavioral assessment instruments available for use with the early childhood/preschool population and because of the desirability of assessing both social skills and problem behaviors with a single measure. The PKBS was standardized with a diverse sample of 2,855 child ratings. Factor analyses indicate the presence of a stable factor structure for both scales. Reliability studies indicate the PKBS has adequate to strong stability. Explorations of within-scale relationships yielded evidence of content validity as well as 2 forms of construct validity. The PKBS appears to be a psychometrically sound and clinically relevant instrument for screening and assessing social skills and social-emotional problems of young children.