A sample of 15,252 basic airmen were administered the History Opinion Inventory (HOI) during basic military training. This 100-item self-report inventory was designed to tap dimensions of school adjustment, family stability, social orientation, emotional stability, bodily complaints, motivations and expectations for achievement, and response toward authority. The service careers of the subjects were then monitored for two years in order to assess the ability of the HOI to predict the criterion of in/out service. An a priori adaptation index developed from HOI items correctly identified as high risk 23 percent of those subjects discharged from service during the two-year period, while incorrectly labeling as high risk only 6 percent of those subjects still in service after two years. The possibility of increasing the accuracy of prediction by utilizing biographic/demographic data is discussed along with the operational usefulness of ths History Opinion Inventory. (Author)