Sulfonamides are the first effective chemotherapeutic agents used for several years to cure or prevent systemic bacterial infections. In addition, this agents showed anti-carbonic anhydrase and cause cell cycle perturbation in the G1 phase, disruption of microtubule assembly, suppression of the transcription activator Nf-Y, angiogenesis and matrix metalloproteinase (MMP). In recent years, novel synthesized sulfonamides have been introduced as antitumor, antiviral and anti-inflammatory agents. In this paper, the cytotoxic effects of 8 synthesized sulfonamides were investigated by MTT assay on HeLa, MDA-MD-468 and MCF-7 cancer cell lines. Human cancer cells were cultured and passaged in RPMI-1640 medium. Cells incubated in 96-well plates in a concentration of 1 × 105 cells/mL for 24 h, and then logarithmic concentrations (0.1 µm, 1 µm, 10 µm, 100 µm, 1mM) of each drug were prepared, added to the plates and incubated for 72 h. Cell survival was then determined using ELISA plate reader in 540 nm applying MTT assay. All tested sulfonamides showed cytotoxic effect on HeLa and MCF-7 cells in the concentration range of 100-1000 µm. These sulfonamides were cytotoxic against MDA-MB-468 cell line at a concentration of 10-100 µm and reduced the cell survival less than 50%. According to the results calculated IC50’s were as following: MDA-MB-468 < 30 µm; MCF-7 < 128 µm and HeLa < 360 µm. In conclusion, some tested sulfonamides had good cytotoxic effects against breast cancer cells, MDA-MB-468 and further investigations are needed to confirm their effects against other cells.