Yeasts in the oral cavities of newborns with thrush can transmit to other patients through devices used for milk feeding. We examined the efficacy of boiling with a domestic microwave oven for disinfection of nipples used by patients with thrush. Nipples, used by three patients with thrush, were cleansed by nursing staff and cultured in tryptone broth with 2% glucose at 37° for seven days. Yeast grew in eight of 17 samples with cleansing and all of 15 samples without cleansing (p=0.001). Next, other nipples used were cleansed and boiled by microwave for ten minutes in a container with one liter of tap water. The nipples were left in the container for an additional 50 minutes or more, and individually cultured similarly. Yeast grew in none of 32 samples with cleansing and boiling, and in 32 of 37 samples without cleansing and boiling (p<0.0001). These findings indicate that the combination of hand cleansing and boiling in a microwave oven is an effective procedure for disinfection of nipples contaminated with yeast and that hand cleansing without boiling can significantly but insufficiently wash the organism off contaminated nipples.