The developmental status of 62 infants with birth weights less than 1,501 g was evaluated at nine or 12 months and at two years of age corrected for prematurity. The mean developmental scores were 99.8 at the first examination and 84.4 at the second, a significant drop (P less than 0.0001). Half of the infants (Group 1) dropped less than 16 points (mean score from 97.1 to 91.3) and half of the infants (Group 2) dropped less than 15 points (mean score from 102.8 to 76.9). The incidence of small for gestational age infants was overrepresented in Group 2. A multivariate analysis revealed that a group of factors including maternal hypertension and diabetes, gestational age, birth weight, and resuscitation at birth correctly classified 87 per cent of the infants into the two groups. The influence of this cluster of medical factors on developmental decline of the very low birth weight infant deserves further consideration.