Objective : Homeopathy is controversial, due to the claims made for very high dilutions. Although several theories are proposed to understand the mechanisms of action, none are scientifically verified. This study aimed to investigate the efficacy of the selected homeopathic medicines in specific in vitro cancer models.Methods : We assessed the cytotoxic activity of selected homeopathic medicines in mother tincture (MT), and ultramolecular dilution (30C, 200C, 1M and 10M) against cell lines deriving from tumors of particular organs, Sarsaparilla (Sars) on ACHN cells (human renal adenocarcinoma), Ruta graveolens (Ruta) on COLO-205 (human colorectal carcinoma), and Phytolacca decandra (Phyto) on MCF-7 (human breast carcinoma). Sars was also tested against Madin–Darby canine kidney (MDCK) cells (a non-malignant cell line). Cytotoxicity was measured using the 3-(4, 5-dimethylthiazolyl-2)-2, 5-diphenyltetrazolium bromide (MTT) method, anti-proliferative activity by trypan blue exclusion assay, apoptosis determined by dual staining the cells with ethidium bromide (EB) and acridine orange (AO) dyes.Results : MTs and ultra-diluted preparations of the three homeopathic medicines had highly significant effects in the respective cancer cell lines, producing cytotoxicity and a decrease in cell proliferation. The effects were greatest with the MTs, but in all cases and persisted, although to a lesser degree in the ultra-diluted molecular preparations. Sars showed no effect on MDCK cells. In the homeopathic medicine treated cultures, hallmarks of apoptosis were evident including, cell shrinkage, chromatin condensation and DNA fragmentation.Conclusion : This study provides preliminary laboratory evidence indicating the ability of homeopathic medicines as anticancer agents. Further studies of the action of these homeopathic remedies are warranted.