Adjudin is a potent blocker of Cl - channels: disrupting Cl - ion transport function results in a decline in sperm capacitation and fertilizing ability in humans in vitro . Adjudin (ADD) is a mitochondria inhibitor. Adjudin is a molecule that mediates adherens junction disruption at the Sertoli-germ cell interface. To investigate the effect of Adjudin on cancer cells, more than ten different types of human or mice cancer cell lines are treated with increasing concentrations of Adjudin and the cell proliferation is measured by the modified MTT assay. Adjudin inhibits cell proliferation in a dose dependent manner in SGC-7901 (human gastric adenocarcinoma cell), MDA-MB-231 (human breast adenocarcinoma cell), Smmc-7721 (human hepatoma cell) and MIA Paca-2 (human pancreatic adenocarcinoma cell) cells. The IC 50 of Adjudin is determined to be 58.0 μM, 13.8 μM, 72.3 μM and 52.7 μM against SGC -7901, MDA-MB-231, Smmc-7721 and MIA Paca-2 cells, res pectively, after treatment for 24 h. Similar results are obtained in other human and mice cancer cell lines. The IC 50 of Adjudin in A549 cells and PC3 cells is 63.1 μM and 93.0 μM, respectively. For WI -38 and BPH-1 cells, the IC 50 of Adjudin can be observed at more than 300 μM and 200 μM, respectively, which is about 5 times and 2 times more than that for the cancer cell lines A549 and PC3.