Cadmium (Cd2+) is a heavy metal and a potent carcinogen implicated in tumor developmentthrough occupational and environmental exposure. However, the auditory effect of Cd2+ is notpoorly understood. The purpose of the present study was to investigate whether prevent theototoxic effects of Cd2+ by antioxidnat in auditory cell line, HEI-OC1. Rosmarinic acid is anaturally occurring phenolic compound and also known to possess marked antioxidantproperties. We showed that antioxidnat inhibited the the cytochrome c release induced by Cd2+.In addition, we showed that the regulatory effect of antioxidnat on apoptosis is through thecaspase-9 activation, and extracellular signal-regulated kinase activation in auditory cells. Theseresults suggested antioxidnat its therapeutic usefulness, against Cd2+ induced activation ofcaspase-9 and ERK.