This paper reports subgroup analysis of a successful cluster-randomized trial to identify attributes of hypertensive patients who benefited more or less from an intervention combining blood pressure (BP) telemonitoring and pharmacist management. The end point was BP < 140/90 mm Hg at 6-month follow-up. Fourteen baseline patient characteristics were selected a priori as subgroup variables. Among the 351 trial participants, 44% were female, 84% non-Hispanic white, mean age was 60.9 years, and mean BP was 149/86 mm Hg. The overall adjusted odds ratio for BP control in the intervention versus usual care group was 3.64 (P < .001). The effect of the intervention was significantly larger in patients who were younger (interaction P = .02), did not have diabetes (P = .005), had high baseline diastolic BP (P = .02), added salt less than daily in food preparation (P = .007), and took 0-2 (rather than 3-6) antihypertensive medication classes at baseline (P = .02). These findings may help prioritize patients for whom the intervention is most effective.