This present study was undertaken to assess the effect of sterilization of the thermometer with three sorts of disinfectant sponges-0.1 % bichloride of mercury sponge 70% alcohol sponge, 0.5% zephiran chloride sponge,- by bacterial culture methods in 10 admitted adult patients in S. Hospital, Mok Po city. The results obtained were as follows ; 1. The thermometer sterilized with 0.1 ％ bichloride of mercury sponge showed no growth of bacteria organism in 5 cases but showed growth of pathogenic organism in 1 case and non pathogenic organism in 4 cases. 2. The thermomerer sterilized with 70 ％ alcohol sponge showed no growth of bacteria organism in 8 cases but showed growth of nonpathogenic organism in 2 cases. 3. The themometer sterilized with 0.5 ％ zephiran chloride sponge showed no growth of bacteria organism in all 10 cases. From these results it could be concluded that 0.5 ％ zephiran chloride would be most effective in sterilization of thermometer.