This study evaluated physician adherence to the Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC 7) hypertension guidelines in 6 community-based clinics. Explicit review of retrospective medical record data for patients with uncontrolled hypertension measured guideline adherence using 22 criteria. Mean overall guideline adherence was 53.5% and did not improve significantly over time. Random-effects models demonstrated significant associations between guideline adherence and various demographic and medical predictors, including age, minority status, comorbid conditions, and number of medications. A subsequent implicit review evaluated the degree to which nonadherence was justifiable and identified factors that might have affected adherence. Nonadherence was rated as justifiable for only 6.6% of the failed explicit criteria. In general, adherence to the JNC 7 guidelines was modest even when barriers that might have affected adherence were taken into consideration.