In India, physicians followed 492 pregnant women attending the prenatal clinics at the 4 city hospitals in Ibadan to examine factors that effect the delivery of infants large for gestational age. None of the women had diabetes mellitus. 10.4% of the women delivered large infants (or= 3800 g). A higher proportion of large infants were born after the rainy season and the harvest season than at other times (15.5% vs. 8.5-10.3%), perhaps due to more variety of and a larger amount of food available at reasonable cost. Large infants were more likely to be delivered via cesarean section than normal weight and low birth weight (LBW) infants (17.6% vs. 4.5% and 9.8%, respectively; p .001). No large infants were stillborn. The stillbirth rate increased as birth weight decreased (0.75% for 2501-3799 g and 4.9% for LBW infants; p .0001). This suggests that large infants are stronger and better equipped to bear the trauma of childbirth. The more weight mothers gained, the greater the incidence of large infants (0 large infants for mothers gaining 0-10 kg, 14.3% for those gaining 10.1-1-15 kg, 21% for those gaining 15.1-20 kgs, and 40% for those gaining 20.1-25 kg; p .001). Maternal height and maternal ponderal index (maternal weight at delivery [kg]/height squared [sq. m]) had a significant positive association with large infants p (p .001 and .0001, respectively). The likelihood of large infants increased with parity (e.g. mothers with large infants, 8.3% for 0 parity vs. 26.5% for parity 6; p .01). Neither maternal education nor socioeconomic class were linked to large infants. These findings demonstrate a need for providers in Nigeria to pay more attention to mothers who gain more than 15 kg in pregnancy, taller mothers, high-parity mothers (- or parity 3), mothers with a high ponderal index, and mothers delivering immediately after the rainy season.