The aim of this study was to investigate the role of the mevalonate pathway in the cytostatic/cytotoxic effects of berberine, a natural plant alkaloid that reduces cholesterol concentration. Berberine as well as lovastatin, an inhibitor of the mevalonate pathway, exerted dose-dependent cytostatic/cytotoxic effects against human breast cancer cells (MDA-MB231). Although the mevalonate pathway metabolites (mevalonic acid, farnesyl pyrophosphate, geranylgeranyl pyrophosphate) effectively reversed cytostatic/cytotoxic effects of lovastatin against MDA-MB231 cells, they were not effective in influencing the cytostatic/cytotoxic effects of berberine. The cytostatic/cytotoxic effects of berberine do not seem to result from inhibition of the mevalonate pathway.