Objective: To investigate the molecular mechanisms by which Qianliening Capsule (前列宁胶囊,QC) treats benign prostatic hyperplasia (BPH). Methods: Human prostate stromal cell line WPMY1 was treated with 0, 1, 3 and 5 mg/mL of QC for 24, 48 and 72 h, respectively, in the presence of 10 ng/mL basic fibroblast growth factor (bFGF). The viability of WPMY1 cells was determined by 3(4,5Dimethylthiazol2yl)2,5diphenyltetrazolium bromide (M'lr) assay. Cell morphology was observed by phasecontrast microscopy. 4',6diamidino2phenylindole (DAPI) staining and fluorescence activated cell sorting (FACS) analysis with AnnexinV/propidium iodide (PI) staining were performed to determine cell apoptosis. The loss of mitochondrial membrane potential was examined by FACS analysis with 5,5',6,6'tetrachloro1 ,l',3,3'tetraethylbenzimidazolylcarbocyadne iodide (JC1) staining. Activation of caspase3 and 9 was evaluated by colorimetric assay. The mRNA and protein expression levels of Bcl2 and Bax were measured by reverse transcription polymerase chain reaction (RTPCR) and Western blotting, respectively. Results: Upon bFGF stimulation, the viability of WPMY1 cells was increased to 122%118% compared with the control cells (P〈0.05). However, treatment with 15 mg/mL of QC for 24, 48 and 72 h decreased the viability of bFGFsUmulated cells to 80%92%, 59%82%, 36%62% compared with the untreated cells (P〈0.05). In addition, QC treatment reduced WPMY1 cell density in a dosedependent manner. Moreover, QC treatment dosedependently induced the loss of plasma membrane asymmetry, the nuclear condensation and fragmentation, collapse of mitochondrial membrane potential, activation of caspase9 and caspase3, and increase of proapoptotic Bax/Bcl2 ratio. Conclusion: Promoting mitochondriondependent apoptosis of prostate stromal cells might be one of the mechanisms by which QC treats BPH.