THE CST WAS CONSTRUCTED BY MCGARRY AND OTHERS AS AN OBJECTIVE, PRELIMINARY SCREENING INSTRUMENT. THREE EXPERIMENTS WERE CONDUCTED TO TEST ITS VALIDITY AND THE POSSIBILITY OF MALINGERING. THE FIRST EXPERIMENT USED 208 MALE FEDERAL PRISONERS, SOME OF WHOM HAD PREVIOUSLY BEEN FOUND COMPETENT, SOME OF WHOM HAD BEEN FOUND INCOMPETENT, AND SOME OF WHOM WERE OF UNCERTAIN COMPETENCY. WHEN CRITERIA RECOMMENDED BY THE TEST'S DEVELOPERS WERE USED, VALIDITY WAS FOUND TO BE MODERATE. THE INSTRUMENT CORRECTLY IDENTIFIED INCOMPETENTS 70 PERCENT OF THE TIME AND INCORRECTLY IDENTIFIED COMPETENTS 27 PERCENT OF THE TIME. COMPETENTS INSTRUCTED TO RESPOND IN AN INCOMPETENT MANNER, HOWEVER, WERE CLASSIFIED AS INCOMPETENT IN 81 PERCENT OF THE CASES. MALINGERING WAS THEREFORE POSSIBLE WITH ONLY MINIMAL INSTRUCTION. THE SECOND STUDY, IN WHICH A SUBSAMPLE OF THE FIRST SAMPLE OF INMATES WAS USED, TRIED TO IDENTIFY MALINGERING INMATES USING A MULTIPLE-CHOICE FORM OF THE TESTS. RESULTS SHOWED THAT MALINGERING INMATES COULD BE IDENTIFIED OVER HALF THE TIME WHILE TRUE INCOMPETENTS WERE FALSELY LABELED AS MALINGERING ONLY 13 PERCENT OF THE TIME. IN THE THIRD STUDY, COLLEGE STUDENTS WERE THE SUBJECTS. RESULTS SHOWED THAT MALINGERING WAS POSSIBLE WITH MINIMAL INSTRUCTION AND THAT INTELLIGENCE TEST SCORES WERE SIGNIFICANTLY RELATED TO THE ABILITY TO PERFORM WELL OR POORLY ON THE CST. RESULTS INDICATED THAT THE CST IS AT BEST A CRUDE DEVICE WITH LIMITED SCREENING ACCURACY AND A NEED FOR REFINEMENT. TABLES AND A REFERENCE LIST ARE INCLUDED. (CFW)