Since 1960, different classes of immunosuppressive drugs have been used in the post-transplant follow-up. Each is assessed for its effectiveness in preventing rejection but also on the basis of the many side effects induced by prolonged treatment. To reduce these side effects, continuous development of knowledge and medical technology to create cutting-edge therapies in the field is necessary. One of these is extracorporeal photochemotherapy (ECP), an immunomodulatory therapy approved by the United States Food and Drug Administration in 1988 for the treatment of advanced forms of cutaneous T-cell lymphoma. EC P is a useful therapeutic tool for the development of immunomodulation supported by CD8+ clone-specific cytotoxic lymphocytes. The T cells targeted by EC P are modified by photoactivation and seem to develop marked immunogenicity with no suppression of the immune response. Recent studies suggest the possible utility of EC P in the treatment of glomerulonephritis and in countering rejection after transplantation of organs including the kidney.