JOBSTART, a federally funded demonstration program, offered basic education, occupational skills training, support services, and job placement assistance to young school dropouts. A study of the impacts of JOBSTART was designed to separate effects of the program from events attributable to other factors. A total of 2,312 people eligible for JOBSTART were randomly assigned: 1,163 to the experimental group and 1,149 to the control group. Thirteen sites conducted random assignments over varying periods of time from August 1985 to November 1987. Follow-up surveys at 12 and 24 months after assignment gathered data on outcomes such as participation in education and training programs, educational attainment, employment, earnings, and use of public benefit programs. An examination of JOBSTART services and participation at the 13 sites found great diversity within the general framework of the guidelines; longer and more substantial participation than that in other programs for young school dropouts; and similar participation hours among different groups and types of sites. JOBSTART had strong impacts on educational attainment--completion of high school or receipt of a General Educational Development certificate. The impacts on employment and earnings were encouraging for mothers; small, but slightly positive, for other women; and generally negative for men. JOBSTART was sometimes effective and sometimes ineffective in yielding second-year labor market gains in brokered programs and in-house programs; it also showed varying success in both concurrent programs and sequential programs. (An executive summary, 64 tables, and 10 figures are provided. Appendixes include additional data tables and 55 references.) (YLB)