ObjectiveTo realize the current status and clinical characteristics of suspected  pneumonia cases of unknown origin (PUO)  in China, so as to  provide the appropriate reference for revising and adjusting the definition of PUO. MethodsOne provincial, one municipal and one county level hospital were selected from 2 provinces participating in the project, clinical data of communityacquired pneumonia(CAP) patients who were hospitalized between April 1, 2008 and March 31, 2009 were collected,  screened and analyzed. ResultsA total of 1 506 CAP case histories  were collected,  442 (29.35%) of which were conformed with PUO definition. The peak incidence season was winter (32.35%); 60.63% were male patients , 57.24% were ≤ 14 years old;  The main clinical manifestations were acute onset, fever, cough, and expectoration, most  patients had promising prognosis (recovery rate>95%), and no clustering events occurred. ConclusionA large part of CAP in inpatients were conformed with suspected cases of PUO, but the clinical course is good. In order to screen out the suspected cases of PUO more specifically and timely, it should be paid more attention to the epidemiological history inquiry into pneumonia cases diagnosed by signs and symptoms or imagings.