A thin-walled Silverman needle has been used for 254 percutaneous punch biopsies of the left ventricle in 198 patients with closed chests at the Cleveland Clinic. The technic is described. The biopsy specimens were adequate for diagnosis in 192 patients. In all but three patients (who had lupus erythematosus, scleroderma, and chronic glomerulonephritis with congestive heart failure) cardiac catheterization and selective cardioangiographic studies were performed. There was angiographic evidence of primary myocardial disease, coronary atherosclerosis, or both, or rheumatic valvular disease in 175 patients. Cardiac catheterization and angiographic studies demonstrated no evidence of organic heart disease in 20 patients.Cardiac tamponade was a complication of myocardial biopsy in eight patients. Post-pericardiotomy syndrome occurred in four patients and ventricular fibrillation in one patient.Myocardium with no pathologic diagnosis and interstitial fibrosis or myocardial hypertrophy or both were the light microscopic findings in 165 patients. Representative sections of the biopsy in 27 patients demonstrated small-vessel disease, basophilic degeneration, focal interstitial myocarditis, amyloidosis, Aschoff's nodules, or vacuolar degeneration. The current experience suggests that myocardial biopsy combined with selective cardioangiography is of experimental value, improves the accuracy of diagnosis, and plays a role in the management of some patients.