The authors examined the relationship between disproportionate intra-uterine head growth, or a relatively small head, and later development, using data collected as part of the Collaborative Perinatal Project of the National Institute of Neurological and Communicative Disorders and Stroke. Within the population of infants who are normal by conventional criteria (term infants with appropriate weight and head-circumference for gestational age), a group with relatively small heads was defined by each of four different methods. Developmental outcome measures included the Bayley Mental and Motor Scales at eight months, Stanford-Binet IQ at four years and Wechsler Intelligence Scales IQ at seven years. No clinically meaningful differences in developmental outcome were found between the infants with relatively small heads and the remainder of the infants.