Performance testing evaluates real-world tasks and skills with a test-display and response environment similar to, or identical with, the job environment. Performance testing offers the promise of providing more comprehensive evidence of construct and predictive validity than knowledge-based testing. This chapter presents information relevant to this promising approach to online testing. First, performance testing is defined and a historical context is presented; a series of test design questions are presented, then validity criteria, standards, and theory are recommended; and two validity-centered design approaches are reviewed. The chapter concludes with a set of implications and conclusions for further investigation.