Two independent studies were conducted to investigate possible differences in General Aptitude Test Battery (GATB) aptitude M resulting from the use of different test equipment (wooden vs. plastic apparatus.) As part of a ten-year longitudinal study of Vocational Development being conducted in the Department of Vocational Education at The Pennsylvania State University, it was decided to administer the GATB to an entire ninth grade class. Because both wooden and plastic pegboards were being used to assess GATB aptitude M, it was decided to compare the scores obtained on the two different types of boards. Results indicate that those students who were tested using the wooden boards performed significantly better than did the students tested on the plastic boards. Converted score differences for aptitude M range from 3 to 26 points with an average difference of 11 points. Stimulated by the initial finding of an average difference of 11 points in aptitude M resulting from the use of plastic vs. wooden pegboards with ninth graders, Trimmer and Klein (1974) replicated the above described study using a sample of 238 adult applicants, including 70 Blacks, as part of routine employment testing in Nevada. In this study, an average difference of 10.5 points was observed. These findings raise serious moral, ethical and legal questions, and therefore it appears to be necessary to either establish norms for the plastic equipment or to discontinue its use. (Author/BJG)