To investigate the effectiveness of mamushi anti-venom, we examined the relationships between the length of hospital stay (LOS) and the anti-venom administration, LOS and intervals of the bite and administration of the anti-venom, and severity of the bite and initial laboratory data. The sample of this study was a total of 46 cases who were admitted for mamushi bite from 2003 to 2013 to our hospital. Data was collected from medical records retrospectively. The average LOS was significantly shorter in those treated with the anti-venom than without the antivenom (6.7 days vs 14.4 days, respectively). Out of the thirty six cases with the anti-venom therapy, the average LOS was significantly shorter if the anti-venom was administered within 6 hours of the bite than when administered after 6 hours (4.8 days vs 10.4 days, respectively). There was a moderate positive correlation between the severity of the bite and increase in ALT initial. Our results suggest that administration of the anti-venom reduces the length of hospitalization, especially when administered within 6 hours of the mamushi bites. A standardized treatment guideline for mamushi bite is anticipated to define appropriate time to administer the anti-venom from the onset, biochemical data to predict severity of the injury at the initial assessment, by collecting patient data.