There is scant information about the etiology and epidemiology of bacterial diseases of infants and children in China because of very little success with bacterial culture. This study describes the severity of abuse of antibiotics among Chinese pediatricians and this abuse's potential interference in determining the etiology of bacterial diseases. According to a survey in Beijing Children's Hospital more than 98% of the patients in the Outpatient Department who were diagnosed with common cold were given antibiotics by physicians. More than one-third of the patients had been taking antibioties before coming to the hospital. Using a sensitive Staphylococcus aureus assay we found that 70% of blood samples and 43% of cerebrospinal fluid samples from the patients with bacterial meningitis and pneumonia contained antibacterial activity. Bacteria were recovered significantly less often from the samples with antibacterial activity than from those who did not from which antibiotic was not recovered, both in blood (5.3% vs. 12.5%) and in cerebrospinal fluid (2.5% vs. 14.8%). This study indicates that antibiotic abuse is a severe problem in China and that judicious use of antibiotics is urgently needed.