The accuracy of a risk index based on reproductive and demographic factors to predict subsequent development was tested with 51 full-term and 53 preterm (birth weight less than 1,501 grams) infants. Stanford-Binet IQ and Reynell Language Expression and Comprehension at 3 years were significantly predicted by this risk index. Socioeconomic status, birth order, and, for the preterm group, severity of illness in the perinatal period were the most significant predictors of developmental outcome. The Home Observation for Measurement of the Environment (HOME) scores were significantly correlated, independently of SES and developmental level, with the 3-year Reynell and Stanford-Binet scores for the preterm, but not the full-term, group. Children who were classified as being at risk at 12 months but who had scores in the normal range at 3 years came from families with significantly higher scores on the HOME scale. Children not detected as being at risk in infancy but whose development was delayed at 3 years came from families with lower scores on the HOME scale. The combination system of perinatal, reproductive, and environmental variables allows the detection of infants at risk for subsequent developmental problems.