Early postoperative infections after transplantation vary according to the transplanted organ. During the subsequent course opportunistic infections such as cytomegalovirus reactivation, Pneumocystis jiroveci pneumonia, invasive pneumococcal infection and mould infections predominate. Reactivated tuberculous infection appears to become more prevalent. Some of the opportunistic infections are preventable by chemoprophylaxis; others can be managed very effectively by monitoring and early preemptive therapy. Physicians caring for patients after organ transplantation need to early consider in the differential diagnosis rare pathogens which are often overlooked with standard diagnostic procedures.