This is a report of the evaluation of the Zambia Safe Water Systems program conducted by The Mwengu Social and Health Research Centre and the Johns Hopkins Bloomberg School of Public Health. The intent of this study was to assess how the Safe Water System was being used in areas where marketing and distribution had focused. Sites were selected on a nationwide basis using distribution information from Society for Family Health (SFH), Population Services International’s (PSI) local affiliate, who ran the social marketing program for CLORIN. A sample size of 1319 households was used, stratifying for type of marketing and household characteristics. For each of these households interviews were carried out among heads of households, primary water caretakers, primary child caretakers and information gathered on children in the household under age five. The fieldwork took place during February and March 2004, which is the end of the rainy season in Zambia. In the study areas, 42% reported current CLORIN use, and 22% said they were past users. The use of CLORIN was increased if the primary water caretaker had a secondary education, and in households of better construction. Households where promotion was carried out by the SFH were more frequent users of CLORIN. Promotion through health centers also had a positive effect on CLORIN use. Of the various marketing strategies, door-to-door promotion was most strongly associated with CLORIN use. Use was also related to the proximity to retail outlets. Although a large number of households were aware of CLORIN through radio and television, this was not associated with increased use. Perception that water was unsafe to drink was a significant reason for starting CLORIN and awareness building of water contamination may be an important message for both CLORIN use and improved hygiene behavior. Chlorine was found in the water of 36% of households who said they had been using CLORIN for a year or more. Rates for households saying they had been using CLORIN for a shorter period of ti