PURPOSE: Antivenin is a standard therapy in snakebite victims. While the required antivenin dose can be easily estimated, based on the initial symptoms, this strategy may be unsuccessful if the initial symptoms progressively worsen. The purpose of this study was to identify the progression rate of the initial symptoms following snakebite and its associated factors. METHODS: The medical records of 44 patients treated for snakebite from give the actual dates of the study period were retrospectively examined. Thirty-two of these patients were enrolled. Demographic data, local wound grade and local effect score at initial presentation (G-0 and LES-0, respectively) and 12 hours after admission (G-12 and LES-12, respectively) were reviewed, along with laboratory data. RESULTS: The 32 patients had an average age of 54.0+/-14.5 years and were predominantly male (n=26) and presented mainly during summer. Compared to G-0 and LES-0, re-evaluated G-12 and LES-12 were significantly increased despite initial administration of proper antivenin dosage (p=0.001 and p=0.000, respectively). Total amounts of antivenin correlated with LES-12 (correlation co-efficiency 0.558, p<0.05). However, factors associated with symptom progression were not revealed. CONCLUSION: Initial snakebite symptoms might progressively worsen within hours despite acceptable initial antivenin therapy. Therefore, re-evaluation within several hours must be considered if when the initial snakebite symptoms are minimal or mild.