We studied the significance of repeated intraperitoneal CDDP administration, as adjuvant chemotherapy, for the prevention of T3 and T4 gastric cancer. Fifty-two patients who had been operated as Curability B were divided into the following two groups, and the data on survival rate, median survival time and interval of "free of recurrence" were accumulated and analyzed. Group A consisted of nineteen patients treated with intraperitoneal CDDP administration and oral anticancer drugs. Group B were treated with systemic chemotherapy. Group A was superior to Group B in comparing the analyzed data. These results suggested that repeated intraperitoneal CDDP chemotherapy for the prevention of T3 and T4 advanced gastric cancer would improve survival rate.