Phototoxicity is a complex phenomenon which may involve photochemical reaction and biological response mechanism. This complexicity and iii mal protecting tendency has led to the development of various in-vitro approaches as sensitive, alternative test to the in-vivo phototoxicity test. In this study, we investigated not only the sensitivity of two microorganism, (C. albicans and 5. typhimurium TA 98 about UV) but also a correlation between in-vitro and in-vivo phototoxicity test using UV A and 1 Furthermore, we studied the effect of irradiation method which were as follows 1) irradiate to material and microorganism, simultaneously 2) irradiate to only material 3) irradiate to material and microorganism, respectively In each irradiation method, it showed no significant difference, However we were able to observe the more sensitive phototoxicity in S. typhimurium TA 98 than C. albicans, and the results of in-vitro test using 5. typhimurium TA 98 had a good correlation with those of in-vivo test.