Our objective was to study the effects of procyanidin on the cell death of human hormone-resistant prostate carcinoma cell line PC-3 and its mechanism. PC-3 cells were treated with procyanidin of different concentrations. The cell apoptosis rates were detected by annexin V-FITC and propidium iodide double staining followed by flow cytometry (FCM) analysis. Mitochondrial membrane potential (Deltapsim) was analyzed by FCM with rhodamine 123 staining. After 24 hours of treatment with 300 microg/mL procyanidin, the apoptosis rate of PC-3 cells was 44.86%, and Deltapsim was significantly decreased by 87.30%. With the extending of procyanidin treatment, the apoptosis rate decreased whereas the necrosis rate increased. Procyanidin could induce apoptosis and necrosis in PC-3 cells, which might be related to down-regulation of Deltapsim.