We have evaluated 48 cases of viper (Agkistrodon halys blomhoffii "Mamushi") bite treated in our hospital from 2001 to 2005. Of all the patients, 21 were bitten in rice field/farm, 10 were in path, 9 were in yard and 8 were in other places. Most cases occurred between July and September. The most frequently bitten regions were fingers and toes. Because swelling reached its maximum at 1.1+/-0.5 day, it was difficult to judge the severity of Mamushi bite by the degree of swelling at the first examination. There was no significant relation between the grade classification of swelling and CPK values. Value of CPK became its peek at 2.0+/-1.1 days after bites. Some reports recommend giving antivenin judging from the grade classification. However we could not estimate the severity of Mamushi bite from the degree of swelling and CPK values at the first examination. The degree of swelling and CPK values at the first examination will not be an index to determine the choice of the treatment including use of the antivenin.