Developed a scale designed to detect invalid response patterns on the High School Personality Questionnaire (HSPQ). Using a large sample of protocols drawn from the HSPQ standardization group, ten items were found to satisfy the necessary criterion for inclusion in the resulting “random” or “validity” (R V) scale. When applied to separate cross-validation groups of nearly 2,000 valid and randomly generated response protocols, RV was found to correctly classify 79% of the profiles. As a further test of the scale's utility, 100 profiles classified as valid and 100 classified as invalid were selected for comparison. In the invalid group, KR-20 reliabilities of the 14 trait scales were almost uniformly lowered. Also, for the invalid group the correlations among the trait scales were attenuated and altered to the extent that the underlying factor structure of the test was upset.