A total of 136 newborns, visited during the period 1980-88, have been studied to evaluate the main factors related to the normalization of weight in preterm babies. They were classified in those who did not achieve a normal weight, those whose normalization was long-lasting (after 40 weeks of postconceptional age), and those with early normalization (before 40 weeks of postconceptional age). Mean-time of the follow-up was 25.7 months, and 96 children achieved a normal weight (70.6%), 104 a normal length (78.8%), and 111 a normal head circumference (86.7%). Preterm babies with a weight under 1,500 g normalize their weight later than those with a greater weight (31 vs 18.5 months p = 0.010). Preterm newborns with early weight normalization had lower morbidity, greater body size at birth and earlier caloric intake. The opposite situation happened in the other two groups. Those without a normalization in the weight have a greater frequency of neurologic sequelae.