Immunohistochemical techniques were used to study the presence of ciclosporin A (CsA) and leukocyte subsets in 36 posttransplant renal biopsy specimens histologically diagnosed as acute graft rejection. Glomeruli from patients with CsA deposits contained more leukocytes (p < 0.05) than glomeruli from tissues without deposits. In contrast, the interstitium from patients without deposits contained significantly more B lymphocytes than interstitia from kidneys with CsA deposits. In both glomeruli and interstitia, the CD4/CD8 ratios were higher in tissues without deposits, although the difference was not significant. The plasma levels of creatinine increased with the intensity of renal CsA deposits, and significantly more patients on hemodialysis had deposits as compared with patients not on hemodialysis. Our findings suggest two types of acute nonvascular rejection: (1) predominantly interstitial, with a good prognosis, characterized by low numbers of intrarenal CsA deposits and a predominance of B lymphocytes and (2) predominantly glomerular, with a poor prognosis, characterized by high levels of intrarenal CsA and a predominance of CD8-positive cells and macrophages.