THE CONTEXT: With the improvement in transplant in surgery, organ storage techniques and immunosuppressive treatments, the number of organ transplant recipients is regularly increasing. To preserve the activity of the graft, immunosuppressive treatment is required for life in most cases, leading to prolonged immunodeficiency. These patients exhibit an increased risk of cancer, notably of tumors associated with viruses such as carcinomas, Kaposi's sarcoma and lymphomas. THE DIFFERENT CANCERS CONCERNED: Cutaneous cancers, notably squamous cell carcinomas, are the predominant cancers encountered in transplant recipients and affect around half of the patients within 20 years following the transplant. Squamous cell carcinomas tend to be multiple, may be life-threatening, and appear to predict the onset of other cancers. Exposure to UV, immunosuppression, the relatively old age at the time of the transplant, light skinned phototype, genetic factors and papillomavirus infections are all factors of risk. Other photo-induced tumors, such as melanoma, some sarcomas or Merkel cell carcinomas also appear increased and of severe prognosis. MEASURES OF PREVENTION: The prevalence of these tumors could be reduced by educating the patients on strict sun-protection measures following the transplant. The factors enhancing Kaposi's sarcoma associated with the HHV8 virus remain to be defined. The possibility of transmission of the infection through the graft must lead to the systematic search for this virus in the donors.