The Chinese herbal preparation denoted PC SPES, a mixture consisting of extracts from eight herbs, is being used with increasing frequency by prostate cancer patients worldwide. Evidence has emerged that PC SPES is an effective modality that alleviates some symptoms in advanced prostate cancer in a significant proportion of patients including the cases that failed conventional therapy. This evidence as well as published data that show the effects of PC SPES in suppressing growth of prostate cancer in animal model studies, is reviewed together with the available data on the possible side effects of PC SPES. The review also covers in vitro studies that reveal the cell cycle specificity, induction of apoptosis, effects on androgen receptor and other molecular and metabolic changes induced by PC SPES that may explain its anticancer activity. Individual chemical components that are present in herbs of which PC SPES is composed, known to have anti-proliferative, antitumor, antimutagenic, analgesic and/or differentiation inducing activity, are listed and discussed. The effectiveness of PC SPES in prostate cancer is explained as due to its complex composition which may target many signal transduction and metabolic pathways simultaneously thereby eliminating the back-up or redundant mechanisms that otherwise promote cell survival when single-target agents are used.