Randomized clinical trials have shown that statins can reduce mortality after acute myocardial infarction (AMI). However, the impact of changes in patterns of statin use, particularly stopping statins, on survival post-AMI is unknown. Our objective was to estimate the extent to which different patterns of statin use are associated with post-AMI mortality. Population-based, cohort study, from 2002 through 2004 in the United Kingdom General Practice Research Database (GPRD), involving patients surviving 90 days after their first AMI. Past statin use was defined as any statin prescription within 90 days before AMI; statin use post-AMI as any statin prescription within 90 days after AMI. Cohort entry was at day 90 post-AMI; subjects were followed for 1 year. Four groups were identified: (i) non-users (patients never on statins); (ii) users (on statins before and continued post-AMI); (iii) starters (started statins after the event); and (iv) stoppers (stopped statins after the event). Hazard ratios (HRs) were estimated using Cox proportional hazards model. The main outcome measure was 1-year all-cause mortality. The cohort included 9939 AMI survivors (mean age: 68.4 ± 12.8 years; 60.3% men), 22.7% of whom were not prescribed a statin post-AMI. When the non-user group (n = 2124) was considered as the reference, the adjusted HRs (95% confidence intervals) of death were 0.84 (0.66-1.09) for users (n = 2026), 0.72 (0.57-0.90) for starters (n = 5652), and 1.88 (1.13-3.07) for stoppers (n = 137). Stoppers of control medications (aspirin, β-blockers, and proton pump inhibitors) were not associated with increased mortality. Discontinuation of statins in survivors of a first AMI was relatively rare in this cohort. However, statin discontinuation was associated with higher total mortality and this may represent a biological rebound or/and a risk-treatment mismatch phenomenon, where treatment is withdrawn from very ill patients. While awaiting further research, at present statin use should only be withdrawn under judicious clinical supervision.