OBJECTIVES It is commonly held that Haemophilus influenzae pneumonia among children in Asia is mostly caused by serotypes other than b (Hib). If so, Hib conjugate vaccines would play little role in the prevention of pneumonia. In two prospective series of children hospitalized for pneumonia in China, the causative agents were searched for with a wide panel of microbiologic assays. METHODS In the university hospitals of Beijing and Hefei, 156 consecutive children 3 months of age and older with symptoms and signs of pneumonia were studied. Blood culture, chest radiograph, nasopharyngeal aspirate for viral antigen detection and paired sera for 20 microbiologic assays were taken. Severity was graded, and the course of illness was monitored uniformly. RESULTS In Beijing only likely contaminants grew from blood cultures, and in Hefei pathogens were identified in two cases. In combined series evidence for bacterial, mixed and viral etiology was obtained in 30, 7 and 21% of cases, respectively. The dominant bacteria were pneumococcus, Hib, Mycoplasma pneumoniae and Chlamydia pneumoniae, responsible for 13, 10, 8 and 8% of cases, respectively. Most patients were treated with extended spectrum antimicrobials such as piperacillin, cefotaxime or ceftriaxone, alone or in combination. One child died. CONCLUSIONS As in most other series from other countries, the leading agent causing childhood pneumonia was pneumococcus but, in line with our previous experience from Beijing, the second most common agent detected was Hib. This observation suggests great potential for pneumococcal and Hib vaccinations in China. Because no evidence supported the need for routine use of extended spectrum antimicrobials, narrower spectrum agents would be safer for patients, would be cheaper for the community and would offer a way to address increasing resistance problems.