Overutilization—defined as the use of health care services for which the benefits do not outweigh the harms—has been identified as one of the leading contributors to the rising cost of health care in the United States. Although informational interventions designed to address overutilization have had a significant, but modest, impact on the rate of overutilization, they have not been sufficient to solve the problem. Also, various psychological mechanisms contribute to the desire for more medical tests and treatments. To effectively address overutilization, we need to better understand the psychological underpinnings of overuse in medicine. The article reviews recent findings from the behavioral science literature—including reliance on anecdotal evidence, test-related affect, the use of diagnostic labels, and medical maximizing tendencies—that lend insight into why patients sometimes seek, demand, or expect medical tests and treatments that are considered by experts to be low value.