The coverage of sewage works is still limited in urban areas of developing counties, although attempts have been made to develop sewage works in those areas. Present household-wastewater treatment (sanitation) facilities such as septic tanks should be utilized until sewage works with adequate wastewater treatment facilities will cover the areas. For the effective use of existing facilities, those should be managed correctly. It has been, however, stated that most of the facilities are not in appropriate conditions. The present household-wastewater management in Hanoi city of Vietnam was investigated by interview with questioners and some keys to utilize present facilities, especially septic tanks, were shown in this study. It was found that 96.5% of flush-toilet holders in Hanoi had septic tanks. Septic tanks are considered to play a major role in household wastewater management in Hanoi city. Although regular removals of septage are one of the fundamental matters to utilize septic tanks, the 95.2% of septic-tank holders had no experience of septage removals. The proper removal of septage is considered to be a crucial issue for utilization of present household-wastewater treatment facilities.