For the purpose to establish the reliability of SRCA using clinical materials, a histological assessment under the suppression of host reaction was introduced; 1) for the immune suppression cyclosporin A (CsA) was used, 2) to overcome the heterogeneity of fragments, the numbers of implants were increased to ten per group (two pieces/kidney), 3) time flame was 6 days as original, 4) the amounts of drugs were essentially similar to those of Bogden's original method. Drugs solely enough to induce immunosuppression such as 5-FU, CPA and MTX were administered by themselves and those not enough such as MMC, ADM and CDDP were done with least enough usage of CsA, 5) histological changes were analysed from three factors such as grade of degeneration (5 grades), tumor cell amounts (3 grades) and numbers of mitosis (3 grades). The histological analysis form representing the numbers of implants of each group on the indicated places by the individual grades of those 3 factors was devised. With this form, chemosensitivity results were expressed as ++, +, +/- and -. In a panel of more than one +/- results a sensitivity ranking was put on. 5) Macroscopic assessment was made by the measurement of height of the implants at day 6 for simplicity only for future relevance. This method of histological SRCA was applied on one parotid, one pancreas and ten colon cancers where viable tumor cells with frequent mitosis were seen in the CsA treated control groups and, on the other hand, occasional apparent degenerations were observed in some of drug treated groups. These facts verified that this histological assessment was practical and rational and covers the disadvantage of macroscopic findings.