In a field experiment involving 120 defendants at Bridgewater State Hospital in Massachusetts, the authors evaluated three instruments for assessing competency to stand trial: the Competency Screening Test (CST), Competency Assessment Instrument (CAI), and Interdisciplinary Fitness Interview (IFI). The CST (a paper-and-pencil test) was administered by a research assistant and scored by trained graduate students. Lawyers, psychologists, and social workers were recruited and trained in the use of the other instruments, then assigned as individuals (CAI) or teams (IFI) to conduct interviews and assess subjects. The performance of the project interviewers was compared against two yardsticks: (1) actual decisions reached by the regular Bridgewater staff, and (2) a consensus of two nationally respected experts who reviewed the cases and formed independent competency judgments. Both the CAI and IFI performed well under these conditions, indicating that one-time interviews by well-trained persons can lead to accurate competency decisions in the majority of cases. The authors conclude that hospitalization for competency assessment is rarely necessary.