A few in vitro methods were developed to compare the result on the phototoxicity of phenothiazines. By the MTT assay, the Candida test, and the RBC photohemolysis, the phototoxicities of UVA and UVB irradiation were measured. This paper presents the comparisons of methods which are effective to measure the phototoxicities of the chemicals causing phototoxicity and photoallergy. The tested chemicals of phenothiazines include Chlorpromazine, Promethazine, Perphenazine, Chlorprothixene, Trifluoperazine and Thioridazine. Each chemical represented variable results according to the test methods. MTT assay shows the most sensitive method.