Data on demographic background and medical diagnosis as well as results of the Missouri Automated Mental Status Examination and items on the Emergency Room Admission Checklist were subjected to stepwise multiple regression analysis to determine their prediction of length of stay of 1233 patients discharged from inpatient treatment programs in Missouri [USA] during the years 1966 through 1971. The correlation between 20 predictor variables and length of stay was 0.38. Involuntary admission, admission while intoxicated, hostility and denial of problems were associated with early dropout, as were unemployment, younger age and having a spouse or someone else to live with.