Background & Aims : We retrospectively examined the incidence of duodenal ulcers (DU) among children in Gunma prefecture over the past two decades, from 1980 to 1999, by data from Gunma University Hospital and its subsidiary hospitals, in order to test the hypothesis that the incidence of DU among children in Japan is decreasing.Method : By our own experience and by the interview to doctors in 23 major hospitals in Gunma prefecture. In addition, to study trends in the prevalence of anti-Helicobacter pylori (HP) infection, we measured anti-HP Ig-G antibody in the serum from children who come to the Department of Pediatrics, Gunma University Hospital during the same period with a complaint because of low body height for a growth hormone secretion stimulating test.Result : We identified 48 children with DU in 1980-1989 and 16 children in 1990-1999. The prevalence of HP antibody showed a declining trend from the 1980s to the 1990s, but there was not a statistically significant difference.Conclusions : The incidence of DU among children in Gunma prefecture is declining recently. Further study is needed to determine whether this is due to the decline in HP infection or not.