Ethanolic extracts of eleven widely used medicinal plants (Withania somnifera, Ocimum sanctum, Sanguinari candensis, Harpogophytum procumbers, Lepidium meyenii, Pygeum africanum, Serenoa repeno, Urtica diocia, Arnica Montana, Citrus aurantium, and Zingiber officinali) were evaluated for their prospective role in tumor regulation based on their ability to modulate growth characteristics of MA-10 Leydig tumor cells. These medicinal plants were chosen because they have been shown to be either potential cyclooxygenase (COX) -2 inhibitors or have been implicated as endocrine disruptors. COX enzymes effectively catalyze the conversion of arachidonic acid (AA) into prostaglandins, AA metabolites released during the inflammatory process. It is this pathway which is believed to play a central role in tumor progression. To assess cytotoxicity, MA-10 cells were treated with various concentrations of each extract (100 ug/ml, 10 ug/ml, 1 ug/ml, 0.1 ug/ml) and cell viability measured by means of both MTT and MTS cell proliferation assays. Ten of the eleven extracts were shown to have comparatively little effect on cell viability at the various concentrations. However, a significant decrease in cell viability was observed in MA-10 cells treated with 100 ug/ml Sanguinari candensis (Blood root). Results were consistent in both MTT and MTS assays. To determine whether the mechanism for this decrease was apoptosis or necrosis, a Caspase-Glo 3/7 Assay was conducted on cells treated with 100 ug/ml Bloodroot. Results of the assay indicated an increase in caspase 3/7 activity, suggesting the decrease in cell viability was due to apoptosis.