Paljin-Hangahmdan is an Oriental herbal formulation under intensive investigation for its ability to modulate growth and survival in cancer cells. This research was performed to study the anticancer effects of Paljin-Hangahmdan water extract (PHWE) in human promyelocytic leukemia (HL-60) cells. After HL-60 cells were routinely cultured, tetrazolium-based colorimetric assay was performed for cytotoxicity test. Cytotoxicity of PHWE (200-800 microg/ml) in HL-60 cells was increased in a dose- and time-dependent manner. However, PHWE (200-800 microg/ml) had less cytotoxicity in peripheral blood mononuclear cells isolated from a healthy subject. To explore the mechanism of cytotoxicity, we used several measures of apoptosis to determine whether these processes were involved in PHWE-induced leukemic cell death. Our results showed PHWE induced the cell shrinkage, cell membrane blebbing, apoptotic body, and DNA fragmentation. In addition, the flow cytometric analysis revealed PHWE (200-800 microg/ml) dose-dependently increased apoptotic cells with hypodiploid DNA contents. These results indicate that PHWE can control leukemic HL-60 cells through apoptosis and may have a possibility of potential anticancer activities.