Purpose: Diabetic foot infection is one of the most common and severe complications of diabetes mellitus that delays healing of the wound. Deep tissue biopsy is considered to be the gold standard method for antibiotic selection in treating infected chronic diabetic ulcers. However, swab culture or superficial tissue biopsy is often performed for a microbiologic test since deep tissue biopsy has limitations in application. The purpose of this study is to find out whether microbiologic results of swab culture or superficial tissue biopsy could be used for selection of antibiotics in treating diabetic ulcers. Methods: This study involved 42 patients with diabetic foot ulcers with negative results in bone probing test. Tissue samples for microbiologic tests were collected from all the patients by using superficial cotton swab, superficial tissue, and deep tissue. The microbiologic results of deep tissue biopsy were compared with swab culture and superficial tissue biopsy statistically. Results: Microbiology of the deep tissue showed the same results with those of the swab culture and superficial tissue in 67% and 71%, respectively. Statistical analysis demonstrated that the microbiology of the swab culture and superficial tissue does not coincide with that of the deep tissue. Conclusion: These results suggest that the microbiology of the swab culture and superficial tissue is not concordant with that of the deep tissue in infected chronic diabetic ulcers. To select appropriate antibiotic regimen, the speci specimen for the microbiologic test should be obtained from deep tissue.