We report on the responsiveness of the SF-12 to changes in quality of life following acute myocardial infarction. Scores at 1, 6, 12, and 24 weeks postdischarge were compared with pre-MI health. Statistically significant differences and standardized response means were examined. Results were compared with the SF-36 subscales and previous reports. Respondents (n = 65) reported the expected poorer physical health at every follow-up, while expected changes in emotional health were observed at 6 but not 24 weeks. Comparison with the SF-36 subscales showed that although the SF-12 reflected the expected pattern of physical health, the summary score obscured an important association between perceptions of general health and participation in usual activities. This information is relevant for developing and evaluating rehabilitation interventions and self-managed recovery following MI. The SF-12 scores obscure important distinctions between quality of life domains, and are therefore not recommended for use following acute MI.