The aim of this study was to analyze the association between maternal age and growth of infants born preterm through the first 4 mo. of age. We prospectively studied 80 infant born at the hospital Herminda Martin in Chilean between January and September 1995 with birthweight < 2500 g and gestational age < or = 36 weeks; those born small for date, with congenital malformations or developing chronic diseases were excluded. The modified Graffar was applied to study socioeconomic status and growth, morbidity and type of feeding was monthly registered at Primary Care Centers where they were controlled. The maternal height was categorized as small (< -1 SD, n = 14), normal (> -1 SD and < +1 SD, 147.6-161.8 cm, n = 52) or tall (> +1 SD, n = 14). Sons from tall mothers presented better W/A z score at 4 mo than those from normal or small mothers (0.85 +/- 0.8 vs 0.31 +/- 0.6, p < 0.03 and 0.85 +/- 0.8 vs 0.15 +/- 0.8, p < 0.04). Length gain through the 4 mo was also better of infants with tall mothers (15.3 +/- 1.4 vs 13.7 +/- 2.3 and 13.6 +/- 2.2 cm, ANOVA p < 0.04), reaching better z-scores (0.2 +/- 0.3 vs -0.7 +/- 0.6 and -0.9 +/- 0.9, ANOVA p < 0.0001). The maternal schooling > 8 y was also associated to infant growth: those with tall mothers presented better L/A z-score at 4 mo than those with normal or small mothers (0.27 +/- 0.3 vs -0.89 +/- 0.7 and -0.85 +/- 0.5 p < 0.001). Exclusive breast milk was present in 7% of tall, 25% of normal and 0% of small mothers. No differences in morbidity were observed between groups. We conclude that Chilean infants born preterm from mothers > 1.61 m present a better growth that those with smaller mothers since the first 4 months of age.