Background With the widespread application of mitral valve reconstructive techniques, systolic anterior motion (SAM) of the anterior mitral leaflet causing left ventricular outflow tract obstruction has been recognized by several groups.SAM occurred in 9.1% of the first 441 patients operated on for mitral valve reconstruction at our institution. Fortunately, SAM subsided with medical therapy within 1 year for a majority of patients as reported in May 1993. Some surgeons, however, have considered abandoning repair for prosthetic replacement after SAM was detected on intraoperative echocardiogram.Methods and Results Since June 1991, a triangular anterior leaflet resection has been cautiously evaluated in patients with extensive anterior leaflet tissue.This has been performed in 23 of 119 patients.Conclusions The frequency of SAM in the 119 study patients has decreased from 9.1% to 3.4%. (Circulation. 1994;90 (part 2):II-195-II-197.)