Immunosuppressive protocols appear to be intensifying, with increasing use of a wide range of biological products (polyclonal, monoclonal, humanized, and chimeric antibodies). Better prophylaxis may so far have contained the infectious complications of transplantation, but infection is still a major clinical burden. The impact of hepatitis C virus has become more widely appreciated because this agent is probably the most common cause of posttransplant hepatitis in all forms of solid organ transplantation. The polymerase chain reaction assay as a rapid diagnostic tool is gradually being introduced into clinical transplantation because of, its phenomenal sensitivity and specificity. Appropriate clinical interpretation of positive results will follow eventually.