Hypertrophic obstructive cardiomyopathy (HOCM), the cause of which is unknown, is a heart disease characterized by obstruction of the left ventricular outflow tract and an increase in interventricular septum thickness. Octreotide, a synthetic analogue of somatostatin, was administered subcutaneously to 15 patients for 6 months in order to determine its efficacy in HOCM. Echocardiographic examination was performed in each patient before we had initiated treatment and after treatment. Interventricular septum thickness, interventricular septum thickness/left ventricular posterior wall thickness, and subaortic gradient decreased significantly at the end of treatment. The ratio of the mitral valve E to A waves increased significantly. We observed that octreotide treatment caused a significant decrease in interventricular septum thickness and subaortic pressure gradient. Before and after therapy left ventricular enddiastolic diameter, left ventricular endsystolic diameter, ejection fraction and fractional shortening were not changed. No adverse effect was observed during the therapy. According to our results, octreotide has some beneficial effects on HOCM and it seems to be a new therapeutic approach for HOCM.