This study compares the inpatient costs of therapy of patients with unstable angina pectoris randomized to surgical or medical therapy at the University of Alabama in Birmingham as part of the National Cooperative Study Group. For 74 patients followed up for 2 years, the mean inpatient charges were $4,728 for 22 medically treated patients, $9,528 for 34 surgically treated patients and $20,215 for 18 patients who crossed over from medical to surgical therapy. Differences among the three groups were statistically significant (P < 0.001). Stepwise multiple regression analysis of total inpatient charges with medical and procedural factors as explanatory variables showed that a history of congestive heart failure, the number of infarctions during the period of the study, the duration of the longest anginal attack, the type of unstable angina and the type of treatment were significant predictors of total inpatient cost, with an R2 value of 0.829 (P < 0.001). These variables explain the cost of treatment. One should not infer that they will also predict the appropriate type of treatment for patients with unstable angina. Although the cost of surgical therapy was double the cost of therapy for patients treated only medically, those medically treated patients whose therapy failed and who subsequently required surgery incurred mean costs twice those of the surgically treated patients and four times those of patients who received only medical therapy. Reassessment of previous criticism of the high cost of surgical therapy is indicated. © 1979.