The effect of isometric handgrip exercise on the systolic murmur and bifid pulse in patients with idiopathic hypertrophic subaortic stenosis (IHSS) was evaluated. During handgrip exercise, the systolic murmur became inaudible or decreased in intensity by auscultation and disappeared or decreased in amplitude in phonocardiographic recordings in nine of nine patients with IHSS. During handgrip exercise, the bifid pulse observed in seven patients with IHSS disappeared or markedly decreased. Handgrip exercise may be helpful in the bedside diagnosis of IHSS.