The Theoretical Advanced Study Institute (TASI) has become the major summer school for advanced students in elementary particle theory in the United States, offering courses in particle theory, phenomenology, and mathematical physics. The theme of the 1990 school, 'Testing the Standard Model', was chosen because of the many new high precision results that had recently become available from the TEVATRON, SLC, and LEP. The goal was to explore the theoretical background and implications of experiments at these and future facilities, both in and beyond the standard model.