The in Vitro chemosensitivity of fibroblast cell strains was determined using a semiautomated tetrazoliurn - based colorimetric assay(MTT assay) to 16 cosmetic materials. This assay is useful method to evaluate toxic effects of the chemicals. From assay results, we determined that the preservatives are more toxic than moisteurizers. The chemicals in the same group have a different toxicity. That is, in preservatives, Germall-115 is more toxic than Danisol - M, - P, and in surfactant, sodium lauryl sulfate than Myrj 52, and in moisteurizers, 1, 3 - butylene glycol is more safe than the others. When the results from this assay for preservatives were compared with patch test results, good correlation was observed. Forthemore, this assay method can be used together with patch test for the evaluation of the chemical toxicity, particularly in cosmetic field.