The possibility that urinary pepsinogen I is a tumor marker of stomach cancer after total gastrectomy was examined. To decide the cutoff level of urinary pepsinogen I after total gastrectomy, urine samples from 15 patients who had undergone total gastrectomy for stomach cancer in the early or advanced stages and had been free from recurrence for more than 5 years were examined by pepsinogen I-specific radioimmunoassay. The mean concentration of urinary pepsinogen I was 17.5 +/- 7.4 ng/ml and the cutoff level of urinary pepsinogen after total gastrectomy was set at 32 ng/ml (mean + 2 SD). Twenty-two of 74 cases who had undergone total gastrectomy for stomach cancer were regarded as positive. And 20 of these 22 positive cases had definite clinical signs of recurrence of stomach cancer. There were only two false-positive cases. These results suggest that urinary pepsinogen I will be an useful tumor marker in detecting the recurrence of stomach cancer after total gastrectomy.