AFTER A REVIEW OF THE HISTORY OF APTITUDE, ABILITY, AND SKILLS TESTING, THE TAXONOMIES OF THE ACTUAL JOB WORLD AND THE TEST WORLD ARE CONTRASTED. THE DEVELOPMENT OF THE CURRENT ARRAY OF TESTING FACTORS IS TRACED THROUGH THE WORK OF BINE, KELLEY, GUILFORD, AND OTHER RESEARCHERS. A SIMILAR DISCUSSION TRACES THE DEVELOPMENT OF MOTOR AND PHYSICAL SKILLS TESTING. PURELY EXPERIMENTAL TEST PROCEDURES ARE CONTRASTED WITH SKILLS TESTS DEVELOPED DIRECTLY FROM WORK PERFORMANCE. AN ANALYSIS OF SEVERAL TESTS DEVELOPED FROM ACTUAL ORGANIZATIONAL SETTINGS FOCUSES ON THE TECHNIQUES USED TO IDENTIFY, RANK, AND VALIDATE JOB-RELATED MEASUREMENTS. SAMPLE DATA COLLECTION INSTRUMENTS ARE INCLUDED. THE NEED TO LINK THE WORLD OF THE TESTING LABORATORY AND THE WORLD OF ACTUAL OCCUPATIONS IS EMPHASIZED. A NUMBER OF STRATEGIES ARE DISCUSSED AND ARE CLASSIFIED ACCORDING TO EMPIRICAL VERSUS INFERENTIAL JUSTIFICATION OF PERSON-JOB RELATIONSHIPS AND MOLAR VERSUS MOLECULAR EXAMINATION OF WORK PERFORMANCE. THESE INCLUDE CLASSIC VALIDATION, OCCUPATIONAL ABILITY PATTERN DEVELOPMENT, RATIONAL SPECIFICATIONS, JOB SAMPLES, BEHAVIOR VALIDATION, SYNTHETIC VALIDATION, AND TASK SAMPLES. SEVERAL OF THE EXAMPLES CONCERN VALIDATIONS OF POLICE DUTIES. ONE TABLE CONTAINS JOB PERFORMANCE DIMENSIONS DERIVED FROM ANALYSIS OF CRITICAL REQUIREMENTS ESTABLISHED FOR POLICE PATROL OFFICERS, INVESTIGATORS, SERGEANTS, AND MIDDLE COMMAND POLICE PERSONNEL. THE DISCUSSION IS AMPLY ILLUSTRATED WITH CHARTS AND FIGURES. FOOTNOTES CONTAIN ADDITIONAL DISCUSSION WHILE REFERENCES ARE APPENDED. (GLR)