Since the inception of the School-to-Work Project in 1998, networks members have increasingly viewed credible evidence as critical to both their approaches to program improvement and their strategies for winning and sustaining support and resources. This issue brief: (1) Describes the activities Network members have pursued together during 1999-2002 that addressed data and evidence concerns; and (2) Draws lessons from the efforts of Network members, as a group and individually, as they have sought to design and implement data and evidence-gathering systems that could help them make their case to others and improve their performance over time. Evaluations of school-to-career initiatives and the contribution of intermediaries have two major goals: (1) Obtaining data to inform improvement; and (2) Securing support and recognition for promising practices and good performance. Designing and carrying out such evaluations is a technical and political challenge. School-to-career intermediaries need to be strategic about the design, timing, and focus of data collection and evaluation efforts. Frequently, intermediaries and their funders and partners want to see too much, too soon. Looking for impacts on student performance indicators before school-to-career interventions are fully implemented or for students with less-intensive school-to-career experiences is a prelude to failure. In considering data collection and evaluation efforts, intermediaries need to match their ambition to available resources and assess best opportunities for using data to build local support. It is critical to define the purpose and the audience for the evaluation work before going too far into the design process: careful planning will avoid either over-designing or under-planning for the cost and complexity of evaluation work. Tracking growth in the types of school-to-career interventions offered and the level of participation provides credible evidence on system building and community support. Customer satisfaction surveys of participating students, teachers, and employers can provide feedback and usable evidence as new activities are put into place and fine-tuned. For those with sufficient resources, assessment of the impact of school-to-career participation on school performance outcomes and community impact can be undertaken for mature interventions. School-to-career intermediaries and their funders and partners value evidence on the nature and worth of what is being done. Intermediaries that do not collect data and evidence may place themselves in a vulnerable position. Although the technical and political challenges of evaluation may seem daunting, intermediaries should look toward building evaluation efforts as they build a school-to-career system. The goal should be to design and implement a data collection and evaluation effort that will be useful, credible, and doable, based on local school-to-career efforts. Youth, District/School, and Employer Participation in School-to-Career Activities of School-to-Career Intermediaries is appended. (Contains 11 endnotes.)