A simple ultrasonic method was used for measuring transplanted kidney volume in 29 patients. Five of these patients developed diabetes mellitus and six women became pregnant following transplantation. Serial measurements were performed over periods of 6-12 months after transplantation. The kidney volume became stable 6 months after transplantation and this volume correlated positively with the renal function. Renal hypertrophy was noted in those transplant patients who developed diabetes mellitus following transplantation and this hypertrophy was associated with improvement in graft function. Transplant volume also rose in acute rejection and returned to normal after appropriate treatment. During pregnancy following transplantation, the transplant volume increased early in pregnancy to return to normal before delivery. This volume increase was also associated with graft function improvement.