Staurosporine, an inhibitor of protein kinase C, is a potential antitumor drug and its derivatives are used as anticancer drugs in clinical trials. Human herpesvirus 8 (HHV-8) is implicated in all forms of Kaposi's sarcoma (KS), primary effusion lymphoma (PEL), and multicentric Castleman's disease (MCD), indicating it to be a DNA tumor virus. It is difficult to culture cell lines derived from KS patients; we therefore used a cell line derived from PEL (BCBL-1) to investigate whether staurosporine affects the HHV-8-related tumors. Our results show that staurosporine treatment reduces the cell viability of BCBL-1 cells and causes cell cycle arrest in the G2/M phase. The G2/M arrest was associated with the decrease in the expression of Cdc2 and cyclin B. Furthermore, the induction of the HHV-8 lytic cycle was not observed under the staurosporine treatment.