This study explored whether the developmental status of 3-year-old prematurely born children could be predicted from the development of sleep-wake behaviors during the preterm period. Sleep-wake states were observed weekly in 71 preterms from the time they were no longer critically ill until term or discharge, and the general linear mixed model was used to model the development of preterm behaviors for both individuals and the group. At 3 years, the home environment and developmental status of 51 children was assessed. Individual infants' deviations from group slopes and intercepts of eight preterm sleep variables were used as predictors. Cluster analyses of the predictor variables were found to relate to Stanford-Binet IQ, language, and fine and gross motor abilities at 3 years post-term. Children in Cluster 4, which showed more rapid active sleep development, averaged higher IQs and better language and fine motor abilities than children in other clusters. © 2004 Elsevier Inc. All rights reserved.