OBJECTIVE Nondipping pattern of circadian blood pressure (BP) is associated with increased cardiovascular morbidity and mortality; however, limited data are available among obese African-Americans. We, therefore, aimed to evaluate the pattern of circadian BP variation and to identify clinical conditions associated with nondipping in this population. METHODS A total of 211 obese African-Americans enrolled in a weight-reduction program underwent 24-h ambulatory BP monitoring. Nondipping was defined as a nocturnal BP reduction of less than 10%. RESULTS Systolic BP (SBP) nondipping was present in 158 participants (74.9%) and diastolic BP (DBP) nondipping was present in 93 participants (44.1%). In multivariate logistic regression analyses, diabetes was associated with SBP nondipping (adjusted OR, 2.53; CI: 1.16-5.76; P=0.02), and increasing BMI (5 kg/m) was associated with DBP nondipping (adjusted OR, 1.46; CI: 1.17-1.83; P=0.001). In linear regression analyses, BMI was positively correlated to office, 24-h, daytime, and night-time SBP (P=0.03, 0.01, 0.03, and 0.005, respectively) and office, 24-h, daytime, and night-time PP (P=0.01, P<0.001, 0.001, and P=0.003, respectively). CONCLUSIONS This study demonstrated an excessively high prevalence of nondippers and independent associations between diabetes and SBP nondipping and between BMI and DBP nondipping in an obese African-American population.