The hypothesis that birth weight predicts blood pressure inversely at age 7 through 11 years was examined in 1,446 white children and black children in Washington Parish, Louisiana. Two data sets of the Bogalusa Heart Study were merged: 1) newborn cohort participants (n = 233), initially examined at birth, 1973-1974, and reexamined in 1984-1985 at ages 9 through 11 years; and 2) subjects examined at ages 7 through 11 years in 1987-1988 (n = 1,213) whose birth weight was collected from birth certificates in 1991. The prevalence ratios for being in the race-, sex-, and age-specific upper decile of diastolic blood pressure in children born with low birth weight (< 2,500 g) versus those with birth weight > or = 2,500 g were 0.85 (95% confidence interval 0.28-2.56) for white boys, 2.66 (95% confidence interval 1.24-5.70, p < 0.05) for black boys, 1.38 (95% confidence interval 0.63-3.03) for white girls, and 1.05 (95% confidence interval 0.40-2.75) for black girls. For systolic blood pressure, the corresponding prevalence ratio for each race-sex group did not differ from one. When the analyses were restricted to full-term births, prevalence ratios in any race-sex group did not differ from one for systolic and diastolic blood pressure. In multiple linear regression analyses, the concurrently determined Quetelet index (p < 0.001) was a much stronger correlate of systolic and diastolic blood pressure after appropriate adjustment than was birth weight (p > 0.05). From this study, there is some evidence that low birth weight may determine a risk for subsequent high blood pressure in black boys in the age group 7 through 11 years, but the inconsistency of the results for other race-sex groups was unexpected and remains unexplained, if the underlying hypothesis is true.