To assess the impact of the initiative, the director of San Francisco's Community Substance Abuse Services convened a group of local researchers. The process evaluation was designed to chronicle the development of treatment on demand as it unfolded in San Francisco and to evaluate over time how closely the initiative met its goals. The capacity evaluation was based on budget documents and admissions data for publicly funded drug abuse treatment in San Francisco for fiscal years 1995-1998. Results of the process evaluation documented the development of the community-oriented Treatment on Demand Planning Council and its efforts to expand treatment, and to create a continuum of services to address the needs of San Francisco's diverse communities, to enhance services, and to prioritize service needs. Results also highlighted the complexities of implementing treatment on demand, including the difficulty of opening new programs. Findings from the capacity evaluation indicated the San Francisco budget supporting publicly funded treatment increased from $32 to $45.2 million over the 1995-1998 timeframe. During the same period, the number of persons entering the system in a single year increased by 18 percent and the number of admissions in a single year increased by 15 percent. Implications of the findings for the design of drug abuse treatment systems using a treatment on demand model are discussed. 18 references and 2 tables