OBJECTIVES: To compare adherence and wastage among 30-day retail program, mandatory 90-day retail program and voluntary 90-day retail program. METHODS: This analysis was conducted using pharmacy claims data from a pharmacy benefit manager (PBM). Patients who were new to either Ace-Inhibitor, statins or SSRIs in March-May 2005 were identified and followed-up for a period of 12-month to measure adherence and wastage. Patients had retail 30-day supply only during the study period were included in 30-day retail program, patients had mandatory 90-day supply during the study period were in mandatory 90-day retail program, and similarly, patients had voluntary 90-day supply were in voluntary 90-day retail program. Adherence was assessed in terms of Medication Possession Ratio (MPR). Medication wastage occurred either when patients switched to different medication within the same class or to similar medication having different strength and that the patient's actual day's supply was less than dispensed day's supply. Medication wastage was measured by the total day's supply wasted among a normalized 30-day period. RESULTS: About 955 patients in 30-day retail program, 148 patients in mandatory 90-day retail program, and 582 patients in voluntary 90-day retail program. Adherence was found to be significantly greater in mandatory 90-day (MPR=0.7543) and voluntary 90-day retail program (MPR=0.6895) when compared to 30-day retail program (MPR=0.3999) (P<0.01). Although medication wastage was found to be relatively higher in mandatory 90-day retail program (2.5 days/30-day-period), followed by retail 30 program (2.3 days/30-day-period) and voluntary 90-day retail program (2.2 days/30-day-period), these comparisons were not significant (P>0.05). CONCLUSION: Adherence was reported to be significantly better for mandatory 90-day retail program and voluntary 90-day retail program than 30-day retail program; while medication wastage showed comparable results across the three programs. This study showed that 90-day supply polices tend to improve the medication compliance without increasing the medication wastage.