Cathepsin D is a lysosomal protease which plays an important role in cancer invasion and metastasis. There are known inhibitors of that enzyme, such as pepstatin and potato inhibitor. In this study, we examined effects of the cathepsin D inhibitor from Vicia sativa L. seed hulls on cell cultures of human skin fibroblasts and breast cancer cells. There is no effect of the D-cathepsin inhibitor from Vicia sativa L. seed hulls on the proliferative activity of either human skin fibroblasts or breast cancer cells, measured by the [3H] thymidine incorporation assay.