BACKGROUND Only one half of Americans have their blood pressure controlled, and there are significant racial differences in blood pressure control. The goal of this study was to examine the effectiveness of 2 patient-directed interventions designed to improve blood pressure control within white and non-white subgroups (African Americans, 49%). METHODS Post hoc analysis of a 2 by 2 randomized trial with 2-year follow-up in 2 university-affiliated primary care clinics was performed. Within white and non-white patients (n=634), 4 groups were examined: 1) usual care; 2) home blood pressure monitoring (3 times per week); 3) tailored behavioral self-management intervention administered via telephone by a nurse every other month; and 4) a combination of the 2 interventions. RESULTS The overall race by time by treatment group effect suggested differential intervention effects on blood pressure over time for whites and non-whites (systolic blood pressure, P=. 08; diastolic blood pressure, P=.01). Estimated trajectories indicated that among the 308 whites, there was no significant effect on blood pressure at 12 or 24 months for any intervention compared with the control group. At 12 months, the non-whites (n=328) in all 3 intervention groups had systolic blood pressure decreases of 5.3 to 5.7 mm Hg compared with usual care (P <.05). At 24 months, in the combined intervention, non-whites had sustained lower systolic blood pressure compared with usual care (7.5 mm Hg; P <.02). A similar pattern was observed for diastolic blood pressure. CONCLUSIONS Combined home blood pressure monitoring and a tailored behavioral phone intervention seem to be particularly effective for improving blood pressure in non-white patients.