A follow-up study of 150 fullterm and preterm infants was conducted to determine the similarities and differences in neuromotor behavior during the first year of life. Three groups (healthy fullterm, healthy preterm, sick preterm) were compared at three, six, nine and 12 months of age. In general, fullterm infants were more similar in their responses to the Neuromotor Behavioral Inventory and more consistently advanced than some preterm infants at all four examinations. The greatest distinction between fullterm and both preterm groups occurred at three and six months. By nine and 12 months fullterm and healthy preterm infants had more similar development, but some sick preterm infants continued to develop differently. It appeared that the influence of prematurity on neuromotor behavior, regardless of whether the infant was healthy or sick, was greatest before nine months of age. After nine months, health appeared to be a contributing factor to the infants' development.