ObjectiveTo understand the risk factors for antimicrobialassociated diarrhea (AAD) in hospitalized children.MethodsClinical data of children with AAD who were hospitalized between， June，2008 and June， 2010 were analyzed.ResultsA total of 4 368 children were investigated, antimicrobial usage rate was 84.96% (3 711/4 368); AAD rate was 29.21%(935/3 201). AAD rate was 35.14% in children ≤1 year of age, which was significantly higher than that of the other groups (P<0.01) ; AAD rate was 27.63% and 41.60% respectively in common illness cases and critical illness cases(P<0.01); AAD rate was 26.39% and 34.01% respectively in children who had received antimicrobial agents for ≤7 days and >7 days respectively(P<0.01); AAD rate was 40.45% in children who had received at least 4 kinds of antimicrobial agents,which was significantly higher than those who had received 1-3 kinds of antimicrobial agents(P<0.01).ConclusionChildren who were small ages,critical sickness, with long terms and frequent use of antimicrobial agents can easily develop AAD . The incidence of AAD can be reduced by rational use of antimicrobial agents .