In our clinical experience, postprandial symptomatic hypoglycemic (PSH) patients with H. pylori gastritis showed a substantial improvement in their hypoglycemic symptoms after the eradication of H. pylori. Therefore, in this study we have investigated whether H. pylori gastritis may contribute to the occurrence of PSH. For this purpose, we have evaluated the following parameters in 12 PSH patients with H. pylori gastritis before and one month after the eradication therapy: (1) the number and severity of PSH attacks that occurred in a one-month period using a 30-day diary, (2) the total symptom score following a mixed meal using a visual analog scale questionnaire (VASQ), and (3) the glucose and insulin responses to the mixed meal. After the eradication of H. pylori, the serum insulin responses at 30 and 60 min decreased (P < 0.001 in both), whereas the plasma glucose levels at 150, 180 and 210 min increased significantly (P < 0.001 for 180 min and P < 0.01 in others) following the mixed meal. The number and severity score of PSH attacks that occurred in a one-month period and the area under curve for symptom score in VASQ decreased significantly (P < 0.001 in all). These results suggest that H. pylori gastritis may contribute to the occurrence of PSH.