Background : The prevalence of chronic obstructive pulmonary disease (COPD) continues to increase worldwide. However, it is often undiagnosed in primary care clinics due to the insufficient use of spirometry.Objectives : Screening spirometry of patients who attended primary care clinics was performed to estimate the prevalence of airflow limitation in general clinics in Akita prefecture.Methods : A total of 1,135 patients 40 years of age and older, who attended general clinics in Akita prefecture, were enrolled in this study. We defined airflow limitation as forced expiratory volume in one second (FEV1) over forced vital capacity (FVC) (FEV1/FVC) < 70% in patients without active pulmonary disease. Patients with possible asthma were excluded according to history of bronchial asthma, symptoms specific to asthma, and answers to a patient characteristic questionnaire.Results : Of the patients in primary care clinics who were 40 years of age or older, prevalence of airflow limitation was 9.2%, of which 88% were undiagnosed as COPD in Akita prefecture. Thus, the widespread use of spirometry in general clinics and improved hospital and clinic cooperation are warranted to reduce the number of undiagnosed COPD cases. Furthermore, we demonstrated that patients with gastric ulcers had a high prevalence of airflow limitation