The Community Hypertension Intervention Project (CHIP) is investigating medical, environmental, and psychosocial factors related to adherence to treatment for hypertension and examining the efficacy of three interventions designed to improve treatment adherence in a high-risk, underserved, ethnically diverse population. There were 1,367 Black (76%) and Hispanic (21%) adults who participated in a 4-year longitudinal study. Participants were randomized to either usual care or one of three interventions: (a) individualized counseling sessions with community health workers (CHWs), (b) a computerized appointment tracking system, or (c) home visits/focus group discussions with CHWs. At baseline, a total of 33% of the participants had one or more comorbidities in addition to hypertension; only 35% had their blood pressure under control. Participants assigned to the patient tracking intervention exhibited the most significant improvement in appointment keeping and blood pressure control status at 6 months; however, the 12-month follow-up assessments indicated that individualized counseling and home visits resulted in significant, sustained improvements in appointment keeping and blood pressure control status. These findings are now being integrated into the patient care delivery system of the participating outpatient clinics.