Fifty-five patients (35 females and 20 males) were studied by noninvasive means 3.5-8.6 years after isolated mitral valve replacement with Models 103 and 104 Beall prostheses. History and physical exams by three physicians, complete hemograms, SMA 18, iron excretion rates, and coagulation profiles were performed. Additionally, electrocardiograms, echocardiograms, phonocardiograms, cardiac series, and high-speed cinefluorography of the prostheses were obtained. Valve wear was assessed by the disc/cage ratio measured from a "three-legged view" with magnification. At a mean duration of 5.85 years after operation, the entire group had a mean disc/cage ratio of operation, the entire group had a mean disc/cage ratio of 0.906 +/- 0.031 vs a normal value of 0.944 +/- 0.014. The group was mildly anemic and had a urinary iron loss that was 40 times normal. The lactic dehydrogenase (LDH) concentration was more than five times normal. The coagulation profiles were abnormal with respect to the bleeding and stypven times, antiheparin activity, fibrin degradation products, and megathrombocyte index. These abnormalities were unrelated to sex, degree of valve wear, and history of thromboembolism. Males were less anemic and had higher urine iron losses than females. Nine patients with severe valve wear (disc/cage ratio less than or equal to 0.87) were significantly more anemic with large urine iron losses and had elevated total bilirubin, serum glutamic oxaloacetic transaminase, and LDH concentrations (ninefold), when compared to nine patients with minimal wear (disc/cage ratio greater than or equal to 0.925). It is emphasized that the findings of a significant anemia, an LDH concentration greater than 1500 mU/ml, and a disc/cage ratio of less than 0.87 in a patient with an isolated Beall mitral valve prosthesis are indicators for the need to replace the prosthesis in the near future. Re-replacement is urged before significant clinical deterioration.