OBJECTIVE: To examine associations between weight gain and changes in blood pressure and the incidence of hypertension in four ethnicity-gender groups.DESIGN: Longitudinal closed cohort studied over an average of 6 y.SUBJECTS: Total of 9309 white and African-American men and women 45–64 y of age who participated in the Atherosclerosis Risk in Communities (ARIC) Study.METHODS: Weight and blood pressure were measured at baseline and after an average of 3 and 6 y of follow-up. Proportional hazard models with weight gain as a time-dependent variable were used to examine the association between weight gain and changes in blood pressure and hypertension. Multivariate models were used with baseline SBP, DBP, age, BMI, height, WHR, smoking, physical activity, education, caloric intake, fat intake and study center as covariates.RESULTS: Weight gain was associated with increases in SBP and DBP in all groups. Hazard ratios for hypertension associated with 1 kg annual weight gain were 1.36 (95% CI, 1.29, 1.45) in white women, 1.12 (95% CI, 1.03, 1.21) in African-American women, 1.35 (95% CI, 1.27, 1.43) in white men and 1.43 (95% CI, 1.27,1.61) in African-American men.CONCLUSION: Weight gain was associated with increased blood pressure and increased incidence of hypertension. The association was weaker among African-American women compared to other ethnicity-gender groups.