A universal feature of all vertebrate cells is their ability to regulate cell volume, which is fundamental in several biological processes such as cell division and apoptosis. Hypotonic cell swelling activates a chloride channel (I_Cl,swell) of unknown molecular identity. This channel is in charge of the Regulatory Volume Decrease (RVD) that allows the cells to shrink back to their original size. TMEM16A is a member of a large family of transmembrane proteins that form receptor activated and calcium dependent chloride channels. Because of the overlapping properties of agonist-induced TMEM16A currents and I_Cl,swell, we ask whether TMEM16A is crucial for RVD. Patch clamp experiments and calcein fluorescence measurements are performed in order to assess hypotonic cell swelling and RVD in HEK293, HT29 and CF-PAC1 cells. Here, we show that in whole-cell patch clamp experiments TMEM16A is activated by hypotonic cell swelling, while suppression of its expression by siRNA inhibits swelling activated currents in HEK293 and HT29 cells. Calcein fluorescence measurements show as well an increase in hypotonic cell swelling and inhibiton of RVD in HEK293 cells treated with siRNA-TMEM16A. These data indicate a contribution of TMEM16A in RVD processes happening upon hypotonic cell swelling.