This study aimed to determine the differences in antibiotic usage patterns in the treatment of acute pyelonephritis according to hospital type and region in Korea.The claims database of the Health Insurance Review and Assessment Service in Korea was used to select patients with the International Classification of Diseases, Tenth Revision code N10 (acute tubulo-interstitial nephritis) or N12 (tubulo-interstitial nephritis, neither acute nor chronic) as the primary discharge diagnosis in 2010-2014. Usage of each class of antibiotics was expressed as the defined daily dose (DDD)/event.The average antibiotic usage per inpatient event was 11.3 DDD. The average antibiotic usage was the highest among patients admitted to tertiary hospitals (13.8 DDD), followed by those admitted to secondary hospitals (11.5 DDD), clinics (10.0 DDD), and primary hospitals (9.8 DDD). According to the geographic analyses, third-generation cephalosporins were highly prescribed in some southern regions; fluoroquinolones and aminoglycosides were highly prescribed in some centrally located regions of the Korean peninsula. The hotspots for carbapenem usage included Seoul and Gyeonggi province cluster and Busan cluster: these regions include the capital city and the second biggest city in Korea, respectively.In conclusion, the antibiotic usage patterns for acute pyelonephritis in Korea differ according to the hospital type and region.