Mitral valve prolapse is an increasingly common etiology among patients presenting for mitral valve surgery. From 1985 through 1987, a total of 457 patients underwent surgery for pure mitral regurgitation. Of these, 304 (67%) had underlying mitral prolapse, 57 (12%) had rheumatic valvulitis, 36 (8%) had underlying ischemic disease, and 22 (5%) had bacterial endocarditis. The anatomic disturbance in the patients with prolapse was chordal rupture in 189 (62%), chordal elongation in 69 (23%), and isolated annular dilatation in 46 (15%). Valvuloplasty techniques were used in 294 patients (64%) overall. Among those with mitral prolapse, 208 patients (68%) underwent reconstructive procedures. Operative mortality for the entire group was 7% and for the valvuloplasty group it was 4%. We conclude that 1. in our patient population mitral prolapse is the most frequent etiology among patients requiring surgery for mitral regurgitation; 2. valvuloplasty techniques are applicable in the majority of these patients; 3. valvuloplasty can be performed with low operative mortality. Over the long term, available results indicate good clinical status and low rates of reoperation and thromboembolic events for patients who have undergone mitral valvuloplasty.