Aims It has been previously hypothesized that the adverse outcome observed in depressed patients after myocardial infarction might be due to an imbalance in autonomic nervous system activity. The aim of this study was to define the role of depressive and anxious symptoms in influencing autonomic control of heart rate after myocardial infarction. Methods and Results The SD of RR intervals, baroreflex sensitivity, and depression and anxiety (Zung’s scales) were assessed before discharge in 103 patients with acute myocardial infarction; 32 were found to be depressed. Among the patients who were not taking β-blockers, those with depression had significantly lower SDs of RR intervals and baroreflex sensitivity than did those without depression (96.3 ± 22.2 ms vs 119.5 ± 37.7 ms, P =.016; 8.6 ± 6.2 ms vs 11.8 ± 6.5 ms/mm Hg, P =.01, respectively). No differences were found when anxiety was considered or when β-blockers were given. Among the patients not taking β-blockers, there was a significant correlation between depression levels and both the SD of RR intervals (r = –0.47) and baroreflex sensitivity (r = –0.40). Conclusions In patients with myocardial infarction, depression but not anxiety negatively influences autonomic control of heart rate. β-Blockers modify these influences. (Am Heart J 2001;141:765-71.)