For the proper antibiotics treatment, identification of pathogen and antimicrobial susceptibility results are mandatory. In Korea, there was no recommendation for microbiological evaluation of community-acquired uncomplicated acute cystitis (CA-UAC) and little microbiological data was available on CA-UAC. Therefore, clinicians have treated CA-UAC based on microbiological data of community acquired uncomplicated acute pyelonephritis (CA-UAPN). In order to evaluate the applicability of CA-UAPNs` microbiological data for CA-UACs`, the comparison of antimicrobial susceptibility test between CA-UAC and CA-UAPN was performed. During 2008, 538 CA-UACs and 1265 CA-UAPNs were collected retrospectively from 14 hospitals (UTI research group) in Korea. Microbiological data were included in 137 CA-UACs (137/538, 25.5%) and 722 CA-UAPNs (722/1265, 57.1%). Escherichia coli was the most common pathogen in both group (83.9% (115/137) in CA-UAC vs. 92.6% (661/722) in CA-UAPN). The antimicrobial susceptibility tests for E. coli between CA-UACs and CA-UAPNs were analyzed. There were significant differences in resistance rates to ampicillin and ampicillin/sulbactam (46.9% vs. 37%, p=0.047; 81.7% vs. 57.1%, p<0.0001, respectively). In conclusion, there are significant differences in ampicillin and ampicillin/sulbactam resistance rates for E. coli between CA-UAC and CA-UAPN. CA-UAC treatment based on microbiological data of CA-UAPN should be cautious and microbiological evaluation for CA-UAC should be considered for proper treatment.