Many anticancer drugs are now available for clinical use. Unfortunately, most are extremely toxic to normal tissue. Use of one or more toxic drugs inactive against the given patient's own cancer may not only deny the patients the benefit of active therapy but may actually make the patient's cancer grow faster. The need for adjuvant chemotherapy can scarcely be doubted. However, distant metastases may be present at the time of primary surgery in many cases. Some form of generalized therapy like drug therapy or immunotherapy must therefore be used to supplement our local form of treatment such as surgery and radiation therapy for cancer. Already the dangers of cancer chemotherapy are reported as adverse effect, not only in the case of advanced cancer patients, but, that of post operative adjuvant chemotherapy. Therefore, predictive assays analogous to antibiotic sensitivity tests are needed to rule out inactive drugs and select active drugs with least toxicity. The treatment of patients with cancer according to the result of tests of sensitivity of cancer cells to anticancer drugs has been introduced many years ago. The examination of the sensitivity is carried out on explanted tumor cells by two different methodical approaches-observation of the cytotoxic effect of the preparation tested to the growth of the tissue culture of the tumor examined, and a short-term examination with the indication of the effect of anticancer drugs according to the decreased utilization or incorporation of the precussors of the synthesis of proteins, RNA and DNA labeled with radioisotopes, or according to the release of enzymes from tumor cells damaged by an efficient anticancer drug. However, clinicians know that there are many disagreements between the sensitivity test and clinical results. Each sensitivity test has its limitation and problems for resolution. Research toward the goal of the sensitivity test is to divise more appropriate method which is simple prompt and precise for drug selection.