Dr. Sharfstein's Introduction: What determines length of stay for psychiatric patients? This is a subject of intense concern in an era of prospective payment and diagnosis-related groups (DRGs). This month's column reports a survey of a broad panel of mental health professionals about the factors that most frequently influence length of hospital stay. Interestingly, the survey respondents considered the patient's symptomatology, level of adaptive functioning, and social supports more important predictors of length of stay than specific psychiatric disorders, or diagnosis, which serves as the basis of the Medicare DRG system. Systematic research on the predictive value of these other clinical factors must proceed so that a more rational per case prospective payment system can be constructed for psychiatry.