This study was conducted to assess a possible alternative method as replacements for in vivo test. The human fibroblasts were exposed to several photoxic chemicals (promethazine, neutral red, chlortetracyclone, amiodatone, bithional, 8-methyooxypsorale) and non-phototoxi substance, ammonium laureth sulfate and irradiatied with 5 J/$cm^2$ of UVA (3320~420nm). The cell viability was measured by NRU (neutral red uptake) assay. The photoxic potential of test chemicals in the NRU PT (phototoxicity test) was assessed by determining the PIF (photoirritancy Factor) by using a cut-off value of 5. The NRU PT responses of most chemicals showed a close agreement with in vivo response except bithinol. There was a relatively good agreement between in vitro NRU assay and in vivo data. These results suggest that NRU assay using fibroblast could be used to predict the phototoxicity.