OBJECTIVES: Noncompliance and non-persistence with long-term medication is a serious world-wide problem that leads to compromised health benefits and serious economic consequences. A systematic literature review was conducted to compare rates of compliance and persistence among studies of treatments for hypertension, dyslipidemia, and diabetes. METHODS: A search of the literature (2000-2005) was focused on publications that provided a numeric measure of medication compliance and/or persistence, an adequate description of methods, and numeric compliance and/or persistence rates for antihypertensives (AHT), lipid-lowering therapy (LLT), or oral antidiabetics (OAD). Studies were classified according to their source of data into pharmacy claims and electronic monitors (Medication Event Monitoring System, MEMS), and by study design into retrospective and prospective studies. Results reported as medication possession ratio (MPR) were extracted and averaged over the treatment arms of the studies. Compliance rates were compared across study design and treatment class. RESULTS: The literature review resulted in 139 studies assessing treatment with one or more targeted medications: AHT=53, LLT=32, OAD=35, multiple treatments=19. Twelve-month compliance rates averaged 67% for AHT, 74% for LLT, and 76% for OAD drugs (overall 72±18%).Compliance rates averaged 79% among prospective and 71% among retrospective studies (NS). Persistence estimates at 12 months from 22 studies ranged between 35% and 92% (mean 63±18%) . Thirty-five percent of the reports related compliance to treatment outcomes. Similar proportions were observed across classes. The proportion of MEMS studies reporting outcomes related to compliance or persistence was higher than studies based on pharmacy claims: clinical consequences (52% vs. 18%), healthcare utilization (14% vs 4%), and lower for no outcome data (33% vs. 78%) (p=0.004). CONCLUSION: These data indicated comparable compliance and persistence rates across treatments for hypertension, dyslipidemia, and diabetes with three-fourths of medication taken as prescribed and two-thirds of patients continuing for one year.