The disposal of household hazardous waste and materials as municipal solid waste (MSW) remains a vexing problem for solid waste managers and policymakers. A major underlying factor is the inconvenience of special collection programs compared to general disposal. A properly designed, mandatory retail take-back program can significantly improve user convenience compared to centralized or periodic, voluntary special collection programs. San Luis Obispo County, California, population 271,960, was the first county in the US to establish a mandatory retail take-back program for specific household hazardous waste and materials (HHWM): fluorescent lamps, household batteries, medical sharps, and latex paint. This program uses retail locations as collection points for subsequent transport by the county to its transfer facility. This shared responsibility program has been highly effective at diverting HHWM from disposal as MSW. Between April 2009 and October 2012 the estimated collection/diversion rates increased dramatically from near zero percent to approximately 36.44% for fluorescent lamps, 21.4% for household batteries, 28.43% for latex paint, and 72.65% for used medical sharps. For household batteries and fluorescent lamps, the convenience of the collection container and the type of store were statistically significant predictors of the number of batteries and lamps collected.