Kaposi's sarcoma is an unusual neoplasm that is seen with increased incidence in transplant recipients. Its occurrence in this group as a tumor is noteworthy in that it may regress spontaneously if immunosuppression is reduced or discontinued. Thus, its response in this setting raises the question of whether it might be best classified as a reversible hyperplasia rather than a true malignancy. In this work we will review recent advances in our understanding of Kaposi's sarcoma, while retaining an historical perspective.