As part of the military recruiting effort, the Department of Defense sponsors surveys of the national youth population to help design recruiting and advertising strategies. This report develops and applies a method of using the information contained in national youth surveys to estimate the probability that respondents taking the Armed Forces Qualification Test (AFQT) would score above the 50th percentile. The method described can be applied for a variety of purposes and provides a means of estimating the proportion of high aptitude youth in the surveyed population. The developed method is applied to selected results from the Youth Attitude Tracking Survey for 1985, the primary survey sponsored on an ongoing basis by the Department of Defense, but it can also be applied to other similar surveys. The method is a two-equation maximum likelihood estimation procedure that accounts for an individual's probability of taking the AFQT and the correlation between error terms in the testing and AFQT equations. Analyses indicate that the AFQT estimation method produces accurate results. Respondents' probabilities of scoring in the desired range are in close agreement with actual test results for the high school and non-high school student models. Thirty-one tables and 4 figures present study data, and there is a 16-item list of references. (SLD)