JFMTC conducted the third adjuvant chemotherapy study for gastric cancer patients after curative surgery from 1982 to 1983. Patients were randomly allocated to one of the three arms by telephone method controlled at the headquarters of the foundation. This method resulted in the marked reduction of ineligible cases (253 cases, 6.0% of 4,236 cases), compared with those in the first study (18.3%). Main reasons of ineligibility were the violation of entry criteria due to the misjudgment of noncancer, duplicate cancers and operative curability. Telephone method for random allocation seems to contribute to the improvement in the data quality of a clinical trial.