A total of 2,052 US high school boys and girls, selected from 10 geographical regions, were tested on consecutive half days using the Armed Services Vocational Aptitude Battery (ASVAB) Form 2 and ASVAB Form 5. Effects of fatigue, training, environment and proctorial variation were minimized by experimental design. An extensive program of optical scanning, computer analysis, intertest comparisons, correlation matrix generation, factor analysis, and equipercentile calculations was conducted. Four factors were identified, with three of the new subtests in the larger battery (ASVAB Form 5) found to be vocationally oriented as opposed to scholastically oriented. Seven subjects common to both batteries had reliability coefficients ranging from 0.56 to 0.76. A new factor in vocational testing, tentatively described as "attention to explicit rules," was identified. (Author)