Two formal validation studies of the Air Traffic Control Specialist Pre-Training Screen (ATCS/PTS), a 5-day computer-administered test battery, are described. The ATCS/PTS was designed to replace the nine-week U.S. Federal Aviation Administration (FAA) Academy ATCS Nonradar Screen program that served as the second major test in the ATCS selection system. Review of ATCS job analyses suggested that predictor tests should assess cognitive constructs such as spatial reasoning and short-term memory, and require dynamic, concurrent performance. A proposed test battery was developed, consisting of two computer-administered information processing tests and a simplified radar-based air traffic control work sample. In study 1, predictive, criterion-related validation (N = 438) found that the proposed test battery explained additional variability in scores earned in the 9-week FAA Academy program, after taking into account student aptitude. In study 2, criterion-related validation (N = 297) demonstrated that the proposed test battery was as valid as the 9-week FAA Academy ATCS Nonradar Screen for predicting progress in field training. Preliminary data from a third study conducted after validation of the ATCS/PTS seem to suggest that the abilities assessed by the new computerized tests reflect the abilities required on the job. However, implementation of the ATCS/PTS for actual employment decisionmaking in June 1992 was based on results obtained in the second concurrent, criterion-related validation study. The U.S. controller selection system since June 1992 has consisted of the four-hour written ATCS aptitude test battery followed by, for those applicants earning a qualifying score and dependent upon agency manpower requirements, second-level screening on the ATCS/PTS. Additional research requirements as part of an aviation human factors research program are described. © 1993 John Wiley & Sons, Inc.**This article is a US Government work and, as such, is in the public domain in the United States of America.