We examined changes in the quality of drinking water stockpiled under various conditions for emergency use. The results indicated that the change in the quality of the stocked water was influenced mainly by the preservation period and not by the amount of water in the bottle. To maintain water quality, the amount of residual chlorine is less important than using sufficiently sterilized water, bottles and caps in the bottling process. Washing the bottles with a small amount of boiling water was not sufficient to ensure complete inhibition of microbial growth.