The advantages of mitral valve repair are well established. Unfortunately, not all valves can be repaired. This presents a dilemma for the surgeon in terms of advising the patient as to the timing of operation and in decision making during operation. Patients requiring correction for pure mitral regurgitation are a heterogeneous group. By classifying the patients according to the cause of mitral regurgitation and the pathologic anatomy, we determined patterns of repair in our surgical practice for 100 consecutive patients with pure mitral regurgitation treated from January 1990 through June 1991. Patients with degenerative valve disease that spares the central portion of the anterior leaflet were likely to undergo valve repair (22/24), whereas those patients with involvement of the central portion of the anterior leaflet were likely to require replacement (15/17). This disparity may be related to the techniques of repair that were used and has spurred us to use other techniques when faced with this problem. Patients with ischemic mitral regurgitation caused by anulus dilatation were likely to undergo repair (15/17), whereas patients with ruptured papillary muscle usually underwent valve replacement (8/9). Operative mortality in this series was accurately predicted by the Parsonnet risk score. Combining knowledge of the expected operative risk and the likelihood of valve repair based on anatomic and pathologic considerations should allow the surgeon to better inform patients of their surgical options.