The MEDLINE database was searched from 1972 to June 2002 to identify studies of interventions designed to improve compliance with antihypertensive or lipid-lowering medications. Studies were required to employ a controlled design, follow patients for >or=6 months and measure compliance by a method other than patient self-report. The literature review yielded 62 studies describing 79 interventions. Overall, 56% of interventions were reported to improve patient compliance. When only those studies meeting minimum criteria for methodological quality were considered, 22 interventions remained and 12 were recommended, because they demonstrated a significant improvement in compliance. Recommended interventions included fixed-dose combination drugs, once-daily or once-weekly dosing schedules, unit-dose packaging, educational counselling by telephone, case management by pharmacists, treatment in pharmacist- or nurse-operated disease management clinics, mailed refill reminders, self-monitoring, dose-tailoring, rewards and various combination strategies. Personalised, patient-focused programs that involved frequent contact with health professionals or a combination of interventions were the most effective at improving compliance. Less-intensive strategies, such as prescribing products that simplify the medication regimen or sending refill reminders, achieved smaller improvements in compliance but may be cost-effective due to their low cost.