The soybean-derived protease inhibitor, Bowman-Birk inhibitor(BBI), is currently showing great promise as a novel cancerchemopreventive agent. In contrast to the wealth of researchconducted on this compound, the anticancer effects of proteaseinhibitors isolated from other leguminous sources have receivedlimited attention. In the current study, 7 protease inhibitor concentrates(PICs) were isolated from various leguminous sources(including soybean) and characterized. The effects of PICs on theproliferation of breast and prostate cancer cells were investigatedin vitro. Chickpea PIC significantly inhibited the viability ofMDAMB-231 breast cancer and PC-3 and LNCaP prostate cancer cellsat all concentrations tested (25–400 μg/ml). In addition, kidneybean (200, 400 μg/ml), soybean (50, 100 μg/ml), and mungbean(100, 200 μg/ml) PICs inhibited LNCaP cell viability. These findingssuggest that leguminous PICs may possess similar anticancerproperties to that of soybean BBI and deserve further study aspossible chemopreventive agents.