A proportion of postcoronary patients seen 16 to 18 months after infarction are seriously depressed (high D score on Minnesota Multiphasic Personality Inventory). A follow-up of 44 such depressed patients showed a significant (p less than 0.001) decrease of standardized D scores, from 80 to 72 units over 4 years of exercise-based rehabilitation. There were associated decreases in scores for hysteria, hypochondriasis, and psychasthenia. A decrease of D score was associated with exercise compliance. An increase of D score was associated with a significant (p less than 0.05) worsening of ST segmental sagging, suggesting that progression of the disease process had contributed to the increase of depression. All of the patients had high (feminine) scores on the masculinity/femininity scale of the MMPI test. This finding was unrelated to the daily running distance or medication; it could represent a "feminine" personality, or be a typical response in a well-educated white collar group. Evidence of successful group interaction may be indicated by reduction in scores for social introversion and schizophrenic traits.