OBJECTIVES: This study aims to explore medical care costs between cases with/without hospital-acquired falls using prospective payment system data according to ICD10. METHODS: We had 23,336 in-patients with more than 16 years old between April, 2010 and March, 2012 at St. Mary’s Hospital in Kurume, Japan. There were 387 injured cases for falls. We examined length of hospital stay (LOS), Falls rate and medical care cost including medication and injection fee during hospitalization. RESULTS: We classified two groups, 387 injured cases with falls and 22,949 cases without falls. The average age (mean ± standard deviation) were 72.0 ± 14.2 years old for cases with falls and 59.7 ±20.3 y.o. for cases without falls. The LOS were 68.3 ±95.4 days and 18.9 ± 28.4 days. According to ICD10, LOS for Mental and Behavioral Disorders (F00-F99) was the longest (61.6 days) and Falls rate was the highest (90.9 1000pt･days). LOS for Factors influencing health status and contact with health services (Z00-Z99) among ICD10 codes and Falls Rate was the lowest (0 1000pt･days) among ICD10 codes. We assessed the highly positive association between length of hospital stay and Falls rate (y = 0.0016x - 0.013, R² = 0.8601). Total medical care cost were 26,971 USD for injured cases with falls and 9,937 USD for cases without falls, medication fee were 565 USD cases with falls and 162 USD for cases without falls, and injection fee were 2002 USD for injured cases with falls and 670 USD for cases without falls. CONCLUSIONS: We realized the length of hospital stay is longer, Falls rate is higher and total medical care cost, medication fee, and injection fee are higher. In order to prevent hospital-acquired falls, we have to make assessments for falls and take an appropriate measure from the viewpoint of ICD10 codes.