Seventy consecutive patients were entered in a two-arm randomized trial after surgical resection for locally advanced gastric cancer. In the first arm, 37 patients were included as a control group, receiving no further treatment after surgery. In the second arm, 33 patients were treated with adjuvant chemotherapy consisting of mitomycin C (MMC), 20 mg/m2 administered intravenously once every 6 weeks for four consecutive cycles. All patients in both arms were followed in the same way for 5 years. At 5 years 23 of 37 patients in the control arm and 7 of 33 patients in the treatment arm were dead because of relapse. Actuarial survival curve was statistically significant in favor of patients given adjuvant MMC (p less than 0.001). After 10 years follow-up, 31 of 37 patients in the control arm and 16 out of 33 patients in the treatment arm were dead because of relapse, the statistical differences continuing in the actuarial survival curve in favor of treated patients (p less than 0.01). The best advantages of adjuvant treatment were observed in the T3N0M0 stage. The most frequent relapse site was the peritoneal cavity and the relapse pattern shows special decrease in liver metastases in treated patients. Toxicity was acute and mild. No delayed toxicity or second malignancies were observed. These data suggest that adjuvant MMC after resected surgery of gastric cancer is a successful treatment and its effects are still evident after 10 years of follow-up.