The relationship between blood pressure control and racial differences in the processes of hypertension care have not been well examined. We reviewed medical records of 15 768 visits to 12 general internal medicine clinics during July 1, 2001 to June 30, 2002 to determine whether visits were adherent to the Sixth Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC VI) by identifying medications selected for hypertension therapy. We compared JNC adherence, blood pressure control, and intensification of therapy by patient characteristics. Using repeated measures logistic regression, we determined the adjusted odds of obtaining blood pressure control when therapy was intensified the visit before, and tested the interaction of intensification of therapy and patient race/ethnicity in predicting blood pressure control. JNC adherence was more frequent among blacks (83.7%) and Hispanics (83%) than whites (78.4%) (P<0.001). Blood pressure was controlled most often among whites (38.7% versus 34.8% for blacks and 33.3% for Hispanics; P<0.001). Blacks (81.5%) and whites (80.9%) were more likely than Hispanics (70.8%) to have therapy intensified (P=0.02). After adjustment for baseline blood pressure, intensifying therapy was associated with higher odds of subsequent blood pressure control (odds ratio, 1.55; P<0.001). There were no significant interactions between race/ethnicity and intensification in predicting control. We found that therapy intensification is associated with subsequent blood pressure control in all racial/ethnic groups and that Hispanics were least likely to have their therapy intensified. Interventions to reduce disparities in cardiovascular outcomes should consider the need to intensify drug therapy more aggressively among all high-risk populations.