OBJECTIVE To evaluate the significance of gastric acid reflux in children with reflux esophagitis (RE). METHODS Twenty-four-hour esophageal pH monitoring and gastroscopy were performed in 180 children suffered from vomiting. The relationship between RE, non-esophagitis (NE), non-erosive reflux disease (NERD) and gastroesophageal reflux (GER) was analyzed. RESULTS Sixty-five of the 180 patients were confirmed as having RE by endoscopy. Among them, the number of cases with grades I, II and III RE according to the diagnostic criteria by endoscopy was 37, 19 and 9 cases, respectively, while the other 115 cases were diagnosed as NE. The positive rate of acid reflux in RE group was 58.5% (38/65), while it was 42.6% (49/115) in NE group (chi(2) = 4.179, P < 0.05). All parameters of acid reflux in RE group except for the episode of reflux and the number of reflux longer than 5 min were significantly higher than those in NE group. None of the parameters of acid reflux except for Boix-Ochoa score in grade III RE patients was significantly higher than that in both grade II and grade I RE cases. However, the difference in acid reflux parameter between grade I and grade II RE patients had not reached statistical significance. The results also showed that the positive rate of pathological acid reflux was 48.3% (87/180). Among them, 38 cases were RE, while other 49 cases were NERD. The difference in acid reflux between these two groups was not significant. CONCLUSIONS Gastric acid reflux may play a major role in the development of RE in children, but may not be a sole pathogenic factor. The degree of acid reflux is not closely correspondent to the severity of RE. Acid reflux may not completely contribute to RE. Gastroscopy is very important for patients with reflux symptom.