Many reports on the diagnostic efficacy of the [13C] urea breath test ([13C] UBT) for the detection of Helicobacter pylori in the residual stomach have shown negative results. We previously reported on the utility of [13C] UBT and conducted an evaluation to establish a standardized protocol with a shorter sampling time for [13C] UBT in partial gastrectomy patients. Sixty-two patients who had undergone partial gastrectomy were included. The [13C] UBT protocol included ingestion of 100 mg [13C] urea, use of mouthwash, and the body in a horizontal position on the left side. The sensitivity of [13C] UBT was 95.7%. Thirty minutes and a cutoff of 2.0 per thousand were found to be optimal for the test, with the body position horizontal on the left side. In the present protocol [13C] UBT appears to be a reliable and convenient tool with the same accuracy rate as other routine tests in patients with a remnant stomach.