In a long-term prospective study, 46 unselected infants born before 35 completed weeks of gestational age were compared with 26 full-term infants. At 4 years of age, 44 preterms and 25 full-terms were available to follow-up. Two preterm children manifested abnormal neurological development, slight spastic diplegia in one case, and psychomotor retardation in the other. Both these cases had already been identified at 18 months of age. Thorough neurological assessment revealed a number of differences between the two groups indicating both delayed neurological maturation and mild dysfunction in the preterms. We drew up a neurological profile to describe these minor neurological signs. The preterms had poorer muscle tone, more spontaneous movements, and were less skilled in certain gross motor functions. They also showed less developed balance reactions, had difficulties in some coordination tests, and asymmetry was more common in neurological functions. In the different subsystems of the neurological profile we also found a greater variation in the preterm group than in the full-term group. There were no significant correlations within the preterm group between the neurological findings at 4 years of age and gestational age, birthweight, and prenatal or perinatal factors.