Photopheresis (ECP) is a new form of photochemotherapy that induces a selective inhibition of the host response to foreign histocompatibility antigens and reverses allograft rejection after organ transplantation. This report describes four adolescent patients with recurrent rejection episodes after renal transplantation, all uncontrolled using standard protocols of immunosuppression (intravenous steroids and OKT3), yet successfully treated with a 6-mo course of ECP. The ECP treatment was performed at weekly intervals during the first month, at 2-wk intervals during the second and third months, and then monthly for another 3 mo. Creatinine clearance improved throughout the treatment in three patients and remained unchanged in one. All patients had a pre-ECP biopsy with a grade 2 or 3 rejection (Banff) with a diffuse infiltrate CD8, CD14, LFA-1 (166 cells positive/0.048 mm2), and VLA-4 (51 cells positive/0.048 mm2) positive, as well as a tubular expression of HLA-DR (6.2 sections of tubule positive/0.048 mm2), ICAM-1, and VCAM-1 (3.1 and 2.9 sections of tubule positive/0.048 mm2). A strong reduction of cell infiltrate and expression of LFA-1 (6.6 cells positive/0.048 mm2). VLA-4 (0.7 cells positive/0.048 mm2), HLA-DR (0.2 section of tubules positive/0.048 mm2), ICAM-1 (0.3 section of tubules positive/0.048 mm2), and a disappearance of VCAM-1 staining were observed in the biopsies performed after 3 mo of ECP. All patients remained rejection-free during ECP, without infections or other complications commonly observed with increasing doses of standard immunosuppression. The clinical improvement allowed a progressive reduction of oral steroids in three of the four patients treated.