The prognosis in chronic myocardial disease is not well defined, partly because of a wide spectrum of clinical courses, and partly because of relatively short observation periods. This paper describes 106 patients followed for 2-12 years. Development or worsening of symptoms after intercurrent infections was associated with a more severe outlook than an insidious debut. The ability to develop myocardial hypertrophy appeared to be an important factor in deciding the prognosis. Pump failure was the cause of death in 80% of the patients, while 16% died suddenly. A favourable course was often noted in patients with ECG signs of left ventricular hypertrophy. This was also the case in patients who developed systemic hypertension. The presence of low voltage, especially in combination with left atrial enlargement, was associated with a malignant development.