Background: The extent to which common life transitions influence medication adherence among patients remains unknown. We examined whether retirement is associated with a change in adherence to medication in patients with hypertension or type 2 diabetes. Methods: Participants in the Finnish Public Sector study were linked to national registers. We included data for the years 1994-2011. We identified and followed 3468 adult patients with hypertension and 412 adult patients with type 2 diabetes for medication adherence for the 3 years before their retirement and the 4 years after their retirement (mean follow-up 6. 8 yr). Our primary outcome was proportion of patients with poor adherence to medication, which we defined as less than 40% of days covered by treatment. We determined these proportions before and after retirement using data from filled prescriptions. Results: The preretirement prevalence of poor adherence to medication was 6% in men and women with hypertension, 2% in men with diabetes and 4% in women with diabetes. Among men, retirement was associated with an increased risk of poor adherence to both antihypertensive agents (odds ratio [OR] 1.32, 95% confidence interval [CI] 1.03-1.68) and antidiabetic drugs (OR 2.40, 95% CI 1.37-4. 20). Among women, an increased risk of poor adherence was seen only for antihypertensive agents (OR 1.25, 95% CI 1.07-1.46). Similar results were apparent for alternative definitions of poor adherence. Our results did not differ across strata of age, socioeconomic status or comorbidity. Interpretation: We found a decline in adherence to medication after retirement among men and women with hypertension and men with type 2 diabetes. If these findings can be confirmed, we need randomized controlled trials to determine whether interventions to reduce poor adherence after retirement could im prove clinical outcomes of treatments for hypertension and diabetes.