In order to determine the indications of chemosensitivity tests against various anticancer agents, clinical trials of 4 different assays, namely; nude mouse isotope assay (NMIA), subrenal capsule assay (SRCA), human tumor clonogenic assay (HTCA) and adenosine triphosphate inhibition assay (ATPA), were performed on 391 patients. Analysis of the correlation between assay results and clinical effects presented the possibility of determining the indications as follows; (1) The positive clinical response of mitomycin C (MMC) should be predicted by ATPA; (2) The clinical tumor resistance against MMC should be predicted by SRCA; (3) Concerning 5-fluorouracil (5-FU) the chemosensitivity test (ATPA) should only be used for the detection of tumor resistance in the assay; (4) The poor results of this study indicated the difficulty of correctly estimating the effects of cyclophosphamide (CPM); (5) The perfect prediction of clinical effects in this trial indicated that cis-DDPlatinum (CDDP) should be estimated by SRCA; (6) The positive clinical tumor response against adriamycin (ADM) should be predicted by SRCA, while the negative one should be predicted by HTCA; and (7) ATPA showed good potential for estimating not only time dependent drugs such as 5-FU, but also cytotoxic drugs.