The 6^th National Population and Housing Census was carried out from October 28 to November 17, 2006 in which three different questionnaires were used. Question number 55 of the 3rd questionnaire asked about Housing Units Sewage Disposal. This paper studies and analyzes the answers to the mentioned question in regional and national levels.

Assessment of housing units sewage disposal conditions shows that the public sewer and cesspools were used commonly by households as sewage disposal places, i.e. major portion of housing units sewage was discharged into the cesspools and the public sewer. About 75.25 and 52.73 percent of the population discharged their toilet and kitchen sewage into cesspools, respectively. Moreover, 22.04 and 23.03 percent of the population discharged their toilet and kitchen sewage into the public sewer, respectively. Considering the public sewer as the main sewage disposal place, provinces Kordestan, Kermanshah and Khuzestan were ranked 1-3, and provinces Kerman and Zanjan were ranked 29-30.