Helicobacter pylori (H. pylori) has expanded to infect about half the world's population. Although there were many studies on the prevalence of H. pylori infection for defined areas in the 1990s throughout the world, there were only limited sources tracking its latest prevalence among large populations. In the present study, we estimated the prevalence of H. pylori among the inhabitants of Nagoya, an urban area of Japan. Study subjects were 5167 participants (1467 males and 3700 females) aged 35 to 69 years from the Daiko Study, a part of the Japan Multi-Institutional Collaborative Cohort Study (J-MICC Study). A urinary anti-H. pylori antibody was used to detect H. pylori infection. The history of eradication treatments for H. pylori infection was obtained using self-administered questionnaires. The prevalence detected by the urinary test included 19.6% (95% confidence interval; 16.8-22.6%) for those aged 35-39 years, 25.8% (23.5-28.2%) for 40-49 years, 39.4% (36.8-42.1%) for 50-59 years, 50.3% (47.8-52.7%) for 60-69 years, and 36.4% (35.1-37.7%). Among 5167 participants, 266 (5.1%) stated that they had received an eradication treatment. Since 167 subjects with negative urinary tests replied that they had been seropositive for H. pylori in the past, they were included among the ever-infected inhabitant group. Consequently, the overall rate of those with a history of persistent infection was 39.6% (38.3-40.9%). The prevalence of H. pylori infection observed in Nagoya seemed to be lower than the corresponding prevalence reported in other studies of Japan. That lower rate might be due to the reduced exposure from improved urban sanitary conditions.