This project investigates the effect of insurance coverage on the length of treatment patients receive in the private practice of psychiatry. Interest is in the implications of changes in length of treatment with insurance coverage for the cost of national health insurance (NHI). Inclusion of coverage for psychiatric care in private practice is a controversial part of proposed NHI plans because of fears of excessive utilization with insurance. There is little evidence to support or defuse these fears. We do not know how psychiatrists and patients behave when patients are insured. The Joint Information Service of the American Psychiatric Association and the National Association for Mental Health has surveyed 10% of psychiatrists in private practice and collected information on each psychiatrist and on 10 each of their patients, including insurance coverage. This large data set is thus a "natural experiment" of the effects of insurance on utilization. Insurance coverage reduces the apparent price to the patient. The basic purpose of this research is to estimate what effect, if any, the price reduction to the patient by insurance has on the length of psychiatric treatment in private practice. This will predict the increase in demand with NHI and thereby lead to a prediction of the total cost of NHI for this specialty. The effect of insurance will be broken down by the type of psychiatrist and the type of patient. Are analytic or nonanalytic psychiatrists more likely to increase utilization with insurance? Are patients with more or less serious disability more influenced by insurance? What diagnoses are particularly affected? This information will guide peer review, or other similar mechanisms, to the most fruitful areas in which costs of NHI can be contained. The effect of insurance and other variables on the length of treatment will be analyzed by multidimensional contingency tables and regression techniques.