This report presents the first direct evidence on the validity of the Naval Postgraduate School Test, Form ZNP. For student officers tested in its first operational use in the fall of 1951 who subsequently entered the Engineering School in 1952, a correlation of .41 was found between test scores and quality-point ratios for the first three terms of academic work. In general, results corroborate earlier studies, although the effectiveness of the tests given "in-the-fleet" in the fall of 1949 was not as great as for tests given at the School, or for the operational form of the selection test. Taken in conjunction with all the other evidence that has been gathered about the validity of tests similar to sections of Form ZNP, the observed effectiveness of this test seems sufficient to warrant its description as a useful instrument for selecting Postgraduate Engineering School students.