An association between vitamin D receptor (VDR) gene polymorphisms and bone mass variance has been observed in adult populations. To analyze possible association between VDR genotype and growth, we studied 589 healthy infants who were homogeneous for age, diet, and vitamin D status. The Bsm I, TaqI, and ApaI alleles' frequencies and genotypes were similar to those reported for Caucasian populations. Variations in Bsm I polymorphism were not associated with calcium intakes nor with serum levels of calcium, 25-hydroxyvitamin D, 1, 25-dihydroxyvitamin D, or alkaline phosphatase activity. But, they were associated with differences in body size. At 2 yr, homozygote BB (BsmI site absent) girls had higher length, weight and body surface area, and inversely, BB boys had lower weight, body mass index and body surface area, than their respective bb counterparts. As a result, gender-related differences were observed in Bb and bb, but not in BB populations. This VDR genotypic effect was observed also at birth and at 10 months in the longitudinal analysis of 145 selected full-term babies homozygous for the Bsm I polymorphism. These findings provide support for the hypothesis that VDR genotype influences intrauterine and early postnatal growth, directly or via interactions with gender-related growth regulators.