Purpose: To evaluate, using ethnomedical data approach, five Indian plants used in traditional medicine for cancer and other diseases for their safety and cytotoxic activity on human lymphocytes. Methods: The antiproliferative effect of the 50, 100 and 200 µg/ml aqueous extracts of five plants (leaves of Phyllanthus niruri, Coleus aromaticus, Azadirachta indica and Camellia sinensis, and dried fruit rind of Garcinia indica) were evaluated in vitro using trypan blue dye exclusion and clonogenic assay methods on two cell lines-Balb/c 3T3 mouse fibroblasts and human peripheral lymphocytes. Results: Among the five plants used traditionally to treat cancer and other infections, two of them (A. indica and C. aromaticus) exhibited cytotoxic effects on lymphocytes. Two other plants (G. indica and P. niruri) exhibited pronounced cytotoxic effects. Another plant (Camellia sinensis) exhibited cytostimulatory effect (> 50 % cell proliferation). For the plants that are traditionally used in anticancer therapy, there was a correlation between the reported use of these plants and their cytotoxic activity on lymphocytes. Conclusion: The plant extracts of the leaves of P. niruri, C, aromaticus and A. indica, and the dried fruit rind of G. indica are cytotoxic to lymphocytes and this lends some credence to their traditional use for cancer treatment. However, green tea (C. sinensis) is cytostimulatory and safe for consumption.