A hundred-forty-one infants born from 26 to 36 weeks, appropriate-for-gestational-age, were followed from birth until the corrected postmenstrual age of 42 weeks. Weight, height and cephalic perimeter were measured on a weekly basis. Based on the average values and percentiles of these measurements it was adjusted a third degree polynomial function. The growth curves obtained, when compared with the so-called intra-uterine growth curves, showed that during the 40th and 42nd postmenstrual weeks the averages and medians are similar. It was observed that the growth dynamics of the preterm infants showed a catch-up pattern in the immediate postnatal period.