This study was purposed to explore the effects of baicalin on proliferation and apoptosis of adriamycin-resistant human myeloid leukemia cell line HL-60/ADR. HL-60/ADR cells were in vitro cultured and its proliferation inhibition was detected by MTT assay. The cell apoptosis was tested by Annexin V FITC/PI double staining analysis, DNA fragmentation and TUNEL labeling method. The expressions of c-myc and bcl-2 mRNA were detected by RT-PCR, and the protein expressions of C-MYC, BCL-2, caspase-3 precursor (procaspase-3), PARP and BAD were determined by Western blot. The results showed that baicalin could remarkably inhibited the HL-60/ADR cell proliferation, the cell doubling time was 48 hours, with an IC50 value of 28 micromol/L. Apoptosis occurred in dose dependent manner (20, 40, 80 micromol/L), and cell apoptosis in earlier and later stages could be detected by Annexin V FITC/PI double staining analysis, DNA fragmentation and TUNEL labeling method. The expressions of c-myc and bcl-2 mRNA in baicalin-treated cells decreased in a time-dependent manner (12, 24, 48 hours). Meanwhile, protein expressions of C-MYC, BBL-2, procaspase-3 and PARP (116 kD) were down-regulated in a time-dependent manner, while the expression of PARP (85 kD) and BAD were up-regulated. It is concluded that the baicalin efficiently induces proliferative inhibition and apoptosis in HL-60/ADR cells. All of above related genes and proteins may be involved in these processes.