The hygiene levels in home laundry operations in Japan have been changing with the changes in lifestyle. Microbial transmission through home laundry has been reported, but mainly in North American and European countries. The home laundering situation in Japan is unique among many countries, and the most characteristic point is that Japanese use the leftover bath water for laundering the next day. However, such a unique custom may cause household microbial transmission. In order to clarify the link between the microbial transmission and the home laundering operation in Japan, a bacteriological investigation of various articles was done. Children's underpants, bath towels, kitchen rags, the washing machine itself and the leftover bath water were investigated. Although variations in bacterial strains were seen, many Staphylococcus spp. were isolated from every sample. Although pathogenic strains were not detected, some opportunistic pathogens were detected. Furthermore, since many bacteria were isolated from bath water, home laundering operations with the used bath water may cause microbial contamination of the laundry.