BR has remarkable effectiveness on canine kidney allograft survival. Its effectiveness in suppression of the immune responses is dependent on the dosage. Atrophy of the spleen and the mesenteric lymph nodes is prominent in treated dogs. Septic complications are slight, with no reduction in the number of peripheral white blood cells. Erosive changes of the mucosa in the entire bowel are the major side effects of the drug treatment. Liver functional abnormality has not been observed.