This paper reports on a longitudinal study of significant influences on the cognitive readiness of a group of children, aged 60 to 66 months. All measures were obtained by prospective study, which began with Apgar scores calculated in the delivery room. Subsequent measures were gathered by individual case studies in homes, with children and examiners matched by race. Tests used were the Preschool Attainment Record, the Peabody Picture Vocabulary Test, the Illinois Test of Psycholinguistic Abilities, and the Wechsler Intelligence Scale for Children. Results of data analysis suggest that readiness considered as cognitive maturity has two contradictory aspects: (1) it is demonstrably influenced by identifiable elements in the preschool years, (2) the degree of influence exerted by identified influences is less than that exerted by unidentified influences. To some extent, all three predictor domains: child, maternal, and environmental data, have a role in shaping readiness. Social class appears to have the greatest influence. (ST)