Chemosensitivity of vinblastin, cisplatin, and mitomycin C were assessed in four different human cancer cell lines (U937, HL-60, CaR-1, and HepG2) by MTT (3-(4,5-dimethylthiazol-2-yl)-2.5-diphenyltetrazolium bromide) assay and the measurement of total cytosolic poly(A)+ mRNA. Results of 12 h mRNA assay with 10 peak plasma concentration (PPC) were significantly correlated with that of standard 3 days MTT assay with 1 PPC. Furthermore, mRNA assay was changed more significantly than MTT assay under cytostatic condition. Because of its minimum culture requirement (12 h) and broad spectrum (cytocidal and cytostatic), mRNA assay will become a useful tool for chemosensitivity test.