In 1975 more than four and a half billion laboratory tests costing more than 12 billion dollars were performed. Accordingly, many pressures have arisen among physcians to justify the use of diagnostic procedures to the public. Because of this and because of the vulnerabilities of human intuition, explicit yet practical models for determining the number of medical tests to perform would be desirable. The objectives of this proposal are (1) to further develop a new method for determining an optimal number of test, interviewers or other procedures to detect illness, (2) to develop practical means for physicians to use this tool, including tables, a pocket calculator program and computer programs, and (3) to explore different means for the collection of data required by the model. Specifically, sixty case summaries from records of crisis clinic patients, half of whom are known to have made a suicide attempt, will be presented to mental health professionals (psychiatrists and psychologists), who will be asked to estimate the likelihood of an attempt, and to estimate other parameters of the model. A comparison will be made between the subjective estimates of clinicians and the predictions of the models for an optimal number of interviewers. Other medical applications of the model will also be explored during the period of support.