This study was conducted to investigate the effects of ascorbic add on their phototoxicity of four phenothiazine derivatives such as chloropromazine, perphenazine, trifluoperazine and thioridazine. Effects of the test compounds on RBes were monitored with a spectrophotometer by the method of Kahan et al. The extent of photohemolysis by chlorpromazine, perphenazine and thioridazine were decreased with the use of ascorbic acid. It was observed that toxic photoproducts were formed by chlorpromazine and thioridazine with preirtadiated. Although red blood cell hemolysis by preirradiated chlorpromazine was decreased with the use of ascorbic acid but thioridazine was not changed.