Risk factors for pulmonary embolism (PE) have been identified among populations in Western countries but have not been well characterized in Japan. A hospital-based case-control design employed cases with PE, which diagnosed by standard imaging techniques; controls were individuals drawn by systematic random sampling from the hospital admission register. A total of 100 (38 males and 62 females) and 199 controls were identified. Patients with PE were younger (56.5 vs 60.9 years) and more likely to be female. The odds ratio ([OR] adjusted for other factors) and 95% confidence interval (CI) for risk of PE was elevated for the following: female gender, prolonged immobilization, history of prior venous thromboembolism (VTE), lower extremity varicose veins, body mass index (BMI) > or = 25 kg/m( 2), extremity paralysis, and gout/hyperuricemia. Inherited thrombophilia was found in 14 patients with PE (14%). Risk factors for PE in Japan are comparable in magnitude to those in Western countries; only one third of PE cases had received VTE prophylaxis.