Uremic patients on hemodialysis for periods in excess of 1 year have a significantly better survival rate for their renal allografts than do similar patients hemodialyzed for less than 1 year. Lymphocytes from the patients of both groups show no difference in response in the mixed leukocyte culture reaction and to nonspecific mitogens such as PHA and PWM. A significant difference between the two groups of patients was observed with regard to their cutaneous delayed hypersensitivity reactions and in their <i>in vitro </i>lymphocyte responses to streptokinase-streptodornase. Patients hemodialyzed over 1 year were anergic to skin test antigens and had a significantly diminished <i>in vitro </i>response to streptokinase-streptodornase. Monitoring of patients for delayed cutaneous hypersensitivity reactions and for <i>in vitro </i>lymphocyte responses to streptokinase-streptodornase may be of some practical value in selecting recipients for renal transplantation.