Phonocardiography was performed in 74 patients with mitral valve prolapse. 24 patients had early systolic clicks ( < 80 msec from S<sub>1</sub>). Four of them had associated systolic murmurs. 30 patients had mid or late systolic clicks ( > 80 msec from S<sub>1</sub>). A systolic murmur followed the click in 13 of these patients. Both an early and mid/late systolic click were noted in three patients. 17 patients did not have systolic clicks. Eight of these patients had holosystolic murmurs and two had late systolic murmurs. Seven patients had ‘silent’ mitral valve prolapse. In summary, early systolic clicks are common in mitral valve prolapse. In many instances the early click is not accompanied by a murmur. Echocardiography is recommended in patients with chest pain or arrhythmia of uncertain etiology, even if characteristic signs of mitral valve prolapse are absent.