By learning about the validity of individual test scores, psychologists can avoid using scores that are invalid and making judgments that are potentially harmful to their clients. This is important not only for improving clinical and forensic practice but also for avoiding lawsuits. In this article, the effective use of projective techniques is described, with attention to the overperception of psychopathology, diagnosis and the description of symptoms, and the detection of child abuse. Guidelines are offered for using the Rorschach, Thematic Apperception Test, human figure drawings, and the Washington University Sentence Completion Test.