We report here a 75-year-old man from South France who developed Kaposi's Sarcoma (KS) 5 months after diagnosis of Philadelphia-chromosome positive chronic myelogenous leukemia (CML). He was found positive for HHV-8 by PCR, negative for both HIV 1 and HIV 2 by serology, and had a normal CD4/CD8 ratio. Favourable evolution of both CML and KS has been obtained with vinblastine and interferon alpha treatment. The patient is currently alive in complete remission of SK and major cytogenetic remission of CML with a 48 month follow-up. Since no immune deficiency could be documented in the patient, this rare observation suggests that CML may have triggered the onset of SK through cytokine release.