IABP is in wide clinical use as an effective adjunctive means for the management of seriously impaired cardiac function. Unfortunately, however, it is an undeniable fact that this specialized circulatory support technic has so far been used in severe heart disease cases in a desultory way, with no established criteria being available for indication of elective IABP for prophylactic purposes. Under such circumstances, it was felt worthwhile to analyze data on preoperative left ventricular function from a series of open heart surgery cases (25 treated with and 94 without IABP) encountered in our hospital since 1983 (when procedure for myocardial protection was virtually standardized) in an effort to formulate acceptable criteria for indication of elective IABP. Hemodynamic parameters studied were LVESVI, LVEF and LVEDP. The results led us to conclude that scheduled IABP can be regarded as indicated for use in each of the following valvular heart diseases if at least one of the respective criteria specified below is fulfilled: MR: LVESVI≥120ml/m², LVEF≤0.4, LVEDP≥21mmHg; AR: LVESVI≥135ml/m², LVEF≤0.4, LVEDP≥18mmHg; MS: LVESVI≥70ml/m², LVEF≤0.35, LVEDP≥23mmHg.