Background: Within the United States, little is known about regional disparities in blood pressure (BP), their changes overtime, or explanations for their existence. Methods and Results: A population-based cohort of 5115 black and white men and women, 18 to 30 years old in 1985-1986 (balanced on age, race, sex, and education), was followed up for 7 years in four centers: Birmingham, Ala; Chicago, III; Minneapolis, Minn; and Oakland, Calif. Differences in elevated BP (EBP) prevalence among centers at years 0, 2, 5, and 7 and in 7-year incidence of EBP were assessed. Sociodemographic and dietary variables, physical activity, weight, smoking, and alcohol were considered. At year 0, no regional differences were seen. Seven years later, there was marked variability in prevalence of EBP overall and for both black and white men, from a low in Chicago (9% for black men and 5% for white men) to a high in Birmingham (25% for black men and 14% for white men). Birmingham also had the highest 7-year incidence (11%) and overall prevalence at year 7 (14%). The adjusted odds ratios, with Birmingham as referent (95% CIs), for 7-year incidence of EBP overall were 0.38 (0.24, 0.60) for Chicago, 0.37 (0.24, 0.57) for Minneapolis, and 0.74 (0.52, 1.07) for Oakland. Conclusions: Regional disparities are absent at baseline but become apparent as the cohort ages. These differences are not fully explained by the available behavioral and sociodemographic characteristics.