TO UNCOVER BASIC PERCEPTUAL AND PERSONALITY DIFFERENCES POSSIBLY RESPONSIBLE FOR DIFFERENCES IN READING ACHIEVEMENT, TWO STRATIFIED SAMPLES OF 60 ABOVE- AND BELOW-AVERAGE READERS WERE SELECTED FROM THE ENTIRE POPULATION OF 5,612 CHILDREN COMPLETING FIRST GRADE IN EDMONTON, ALBERTA, CANADA. THE GROUPS WERE MATCHED ACCORDING TO SEX, SCHOOL, GROUP INTELLIGENCE SCORES, AND, IN 25 OF THE 30 PAIRS, TO THE FIRST-GRADE TEACHER. SEVEN MEASURING INSTRUMENTS WERE USED--THE EDMONTON PUBLIC SCHOOL WORD RECOGNITION TEST, THE GATES PRIMARY READING TESTS, THE MARIANNE FROSTIG DEVELOPMENTAL TEST OF VISUAL PERCEPTION, THE WEPMAN AUDITORY DISCRIMINATION TEST, THE PEABODY PICTURE VOCABULARY TEST, THE STANFORD-BINET TEST, AND A FIVE-POINT RATING SCALE ADAPTED BY THE INVESTIGATOR AFTER MALMQUIST TO MEASURE CONCENTRATION, PERSISTENCE, AND DOMINANCE/SUBMISSIVENESS. THE MAIN ANALYSIS USED WAS THE MULTIPLE LINEAR REGRESSION DEVELOPED BY BOTTENBERG AND YOUNG. SIGNIFICANT RELATIONSHIPS WERE FOUND BETWEEN SEVERAL FACTORS--PERCEPTUAL, INTELLECTUAL AND PERSONALITY--AND EARLY READING ACHIEVEMENT. A BATTERY CONSISTING OF THE FROSTIG DEVELOPMENTAL TEST OF VISUAL PERCEPTION, THE WEPMAN AUDITORY DISCRIMINATION TEST, AND A TEACHER'S RATING FOR PERSONALITY TRAITS, PARTICULARLY CONCENTRATION, APPARENTLY HELPED DIAGNOSE PERCEPTUAL AND PERSONALITY WEAKNESSES WHICH MIGHT UNDERLIE PRIMARY READING DEFICIENCIES. THIS PAPER WAS PRESENTED AT THE INTERNATIONAL READING ASSOCIATION CONFERENCE (SEATTLE, MAY 4-6, 1967). (RH)