From July 1985 through September 1987, the County of San Diego, California, operated the Saturation Work Initiative Model (SWIM) as a demonstration project. The demonstration tested the feasibility and effectiveness of requiring ongoing participation in employment-related activities by a high proportion of persons on welfare. SWIM provided job search and unpaid work experience. SWIM also included some of the features emphasized in the Job Opportunities and Basic Skills Training (JOBS) program of the Family Support Act of 1988: the program required ongoing participation as long as people remained on welfare, had monthly participation goals, and included education and training among its services. One goal of the SWIM demonstration was to determine whether the program had an impact on employment and welfare dependence and whether the approach proved cost-effective. The random assignment research design included a sample population of 2,312 recipients of Aid to Families with Dependent Children in the experimental group and 2,302 in the control group--two-thirds of all who registered during the first year of SWIM. The study found that SWIM's effects on employment, earnings, and welfare receipt were encouraging, particularly for single parents who were already receiving welfare when they came into the program, and principal earners in two-parent welfare cases. For the single parents, SWIM produced gains in employment and earnings that were larger than those observed in any study of a program serving the full range of Work Incentive-mandatory caseload. For the principal earners (primarily male) in two-parent households, SWIM provided the first evidence of sustained earnings gains. For both groups, SWIM also resulted in notable welfare savings. (54 references.) (KC)