A multicenter prospective cohort study to assess the occurrence and characteristics of acute Q fever associated with community acquired respiratory infections was performed. Among the 400 patients enrolled for the study, 10 (2.50%) patients (5 out of 120 cases of pneumonia, 3 out of 131 cases of acute bronchitis, and 2 out of 149 cases of upper respiratory infections) were diagnosed as having acute Q fever. Contact with dogs or cats before the onset of the disease was confirmed in most of the patients. The clinical profiles of these 10 patients were generally similar to those reported from other countries, such as fever, general fatigue and liver dysfunction, except for the predominance of sporadic cases among the urban population. Our study demonstrates that Q fever is not uncommon cause of community-acquired respiratory infections even in Japan.