A study was performed to compare the influence of pregnancy weight gain on infant birth weight and outcome among two groups of indigent women from the rural South: those who were highly overweight before pregnancy (greater than or equal to 135%) and those who were of average weight (90% to 120% of standard weight for height). The groups had comparable numbers of black and white subjects. Pregnancy weight gain affected birth weight in the average-weight group but did not significantly affect birth weight in the highly overweight group. Infant outcomes for both groups were similar. These findings suggest that consideration should be given to not requiring a minimum weight gain for women whose degree of overweight equals or exceeds 135% of standard body weight for height.