Summary Five renal homotransplant patients on the Metabolic Ward of the University of Colorado Medical Center were studied preoperatively and postoperatively. Nitrogen balance data accumulated on these patients indicated that azathioprine had no notable effect upon the balance. These patients were severely depleted prior to therapy. Prednisone administration resulted in an increased nitrogen excretion; however, the patients returned to a stable nitrogen balance near equilibrium despite the continued administration of rather massive daily doses of prednisone. The findings indicate that a gain in protein stores rather than continual depletion is possible even with long term massive prednisone and azathioprine therapy. Evidence is also presented that prednisone exerted a rather significant catabolic effect upon endogenous protein stores in homograft patients in addition to any anti-anabolic effect it may have exerted. Finally, it was noted that with the massive nitrogen intakes, the patients exhibited an apparent decrease in efficiency of absorption by the gastrointestinal tract. As a result, the fecal nitrogen output was found to be well in excess of normal values.