An operative approach to the ventricular aspect of the aortic valve has permitted combined prosthetic replacement of the aortic and mitral valves. In the first clinical trial of the method, the patient recovered promptly from the surgery and was dramatically improved. This operative technique, which was developed in the experimental laboratory, consisted of a left thoracotomy, left atriotomy, and excision of the mitral and aortic valves, followed by insertion of caged-ball valve prostheses in both areas. Final evaluation of this new approach will depend on further carefully controlled clinical trials and on objective evaluation of the long-term results.