Patients who suffer from post-infarction depression are a high risk group with an increased mortality risk. The reasons for this are not known although it may be because such patients cannot cope with the chronic condition of cardiac disease. We designed a profile of clinical and behavioural outcome measurements representing recovery after myocardial infarction. 552 male survivors of acute myocardial infarction (29-65 years; mean = 53) were grouped at study entry according to their depression status. 377 patients were reassessed after 6 months and were divided into the following subgroups: 50 (13.3%) patients had severe depression; 85 (22.5%) moderate depression and 242 (64.2%) low degrees of depression in the initial study. There were no substantial differences in baseline characteristics between the index group and the drop-out group. The unadjusted relative risk for follow-up angina pectoris among patients with depression (severe versus low) was 3.12 (95% CI 1.58 to 6.16) and was 5.55 (CI 2.87 to 10.71) for emotional instability. The relative risk for maintenance of smoking habits was 2.63 (CI 1.23 to 5.60) and was for work resumption 0.39 (CI 0.18 to 0.88). There was no association between depression and the occurrence of late potentials. After adjustment for univariate variables (age, social class, recurrent infarction, helplessness) only small and nonsignificant changes in the relative risks were found. However the inverse association of depression and work resumption was lost after adjustment. The investigation revealed that persistent postinfarction depression is an independent and important source of subsequent morbidity and long-acting reduced quality of life. Depression has adverse effects on illness behaviour and pain perception.