Salicylanilides possess a wide range of biological activities. A new mechanism of action of these compounds was discovered in 1998. They act as inhibitors of the two-component regulatory system (TCS) in bacteria. Conventional anticancer treatments are nonspecific to target killing of tumor cells, may induce severe systemic toxicity and produce drug resistant phenotypic growth. The aim of our study is determining antiproliferative effect of salicylanilide which is known as anthelmintic generally. In our experiments, antiproliferative and cytotoxic effects of different concentrations (400, 200, 100, 50, 25, 12.5, 6.25, 3.125, 1.56 and 0.78 ?g/mL) of salicylanilide investigated on A549 human non-small lung cancer cells, Caco2 human colon cancer cells and MCF-7 human breast cancer cells. 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyltetrazolium bromide MTT assay was performed on mitochondrial activity levels to observe cytotoxic effects on A549, Caco2 and MCF7 cells for 24 hours. As a result the required concentration to inhibit the cell growth by 50% (IC50) on A549, Caco2 and MCF7 cells for salicylanilide was 260.93 ?g/mL, 201.64 ?g/mL and 292.66 ?g/mL after incubation for 24 h, respectively. If these results are supported further molecular investigations, it may be a new approach for the treatment of lung, colon and breast cancers.