Medical teams are keenly aware of the need to evaluate health care quality and the cost/benefit ratio. We prospectively applied three proposed indexes, designed for predicting mortality, for evaluating disease gravity, and for evaluating health care in intensive care patients, in two populations of patients undergoing heart surgery.From January to June 1991, 243 patients (mean age 58.1; 55 females, 188 males) underwent coronary bypass surgery (n = 116; mean number of bypasses = 2.94 per patient) or valve replacement (n = 127). The patients were divided into 3 groups of increasing gravity on the basis of the preoperative presentation (Groups 1, 2 and 3 for Parsonnet's index, a specific index for predicting mortality in patients with acquired cardiopathies undergoing heart surgery = 0-9, 10-19 and > 20 respectively). A comparison was then performed for each population (bypass surgery and valve replacement) between the predicted mortality and the APACHE II index of disease gravity and the OMEGA index of intensive care.Overall mortality was 3.7% (2.85% in the bypass population and 4.72% in the valve population). The specific Parsonnet index (PI) for cardiac surgery gave a good indication of mortality risk (observed deaths 0.7% for PI = Group 1; 2.6% for PI = Group 2; 13.1% for PI = Group 3) and of postoperative morbidity since inotropic support was required in 18, 45 and 59% for PI Groups 1, 2 and 3 respectively. For patients in the PI Group 3, postoperative care in the intensive care unit lasted > 3 days and required ventilatory support for > 24 hours. APACHE II and OMEGA did not contribute to evaluating the Parsonnet index.A high risk population undergoing cardiac surgery can be defined among patients with a Parsonnet index above 20. Under this threshold, the risk of mortality falls to 1.4%.