A study examined the relationship of aptitudes to the performance of skilled technical jobs in engine manufacturing. During the study, several approaches were utilized, including criterion-referenced validation, taxonomic validation, construct validation, and detailed anlaysis of the behaviors involved in performing the jobs. The study sample consisted of 224 employees who performed 28 technical jobs related to engine manufacturing. Researchers concluded that performance in these jobs is best predicted by the following aptitude components: verbal reasoning (measured by reading comprehension, logical reasoning, and figure-series tests), spatial ability, clerical speed, manual dexterity, academic ability (measured by tests of induction and numerical ability), and visual pursuit. Furthermore, the technicians averaged higher than the general population on most of the tests measuring abilities that predict success on the job. While the validity coefficients found in the study are reduced in size by the restricted range of job performance and job ability in the sample, it is reasonable to expect that they would have been higher if a broader range of aptitudes and job performances were represented in the sample. (The test instruments used and guidelines concerning their use are provided in appendixes and in an attached supplement.) (MN)