OBJECTIVES: To evaluate the patterns and predictors of adherence to statin therapy in all patients with diabetes in the community. METHODS: We retrospectively studied patients with type 1 and type 2 diabetes who were resident in Tayside, Scotland from 1st January 1993 to 31st May 2003, with at least 6 months of prescriptions of statins. The main outcome measure was an adherence index. The influence of several covariates including age, sex, duration of diabetes, adherence to diabetes medication and co-morbidities were also assessed. RESULTS: A total of 5010 patients were included in the study: 4816 with type 2 diabetes and 194 with type 1 diabetes. Median statin adherence was 75% and 77% in type 1 and 2 diabetes respectively, with a similar distribution in both groups. There were 35% of type 1's and 42% of type 2's with adequate adherence (°Ý80%). Predictors of adequate adherence in type 2 diabetes were being older, being an ex-smoker compared to never having smoked, better adherence to diabetic medication, a lower HbA1c level, shorter duration of statin therapy, a history of coronary heart disease, a history of stroke and being prescribed concurrent medication for cardiovascular disease. Conversely, patients prescribed concurrent asthma medication were less adherent to their statin medication. In type 1 diabetes significant predictors were better adherence to diabetic medication, a lower HbA1c level, being female and being prescribed concurrent medication for cardiovascular disease. CONCLUSIONS: Approximately 65% of type 1 patients and 58% of type 2 patient collected less than 80% of their medically recommended dose of statins. Given the increased risk of coronary heart disease facing patients with diabetes this poor adherence could have significant health implications.