FIVE STUDIES ARE REPORTED OF OPERANT CONDITIONING AND LANGUAGE DEVELOPMENT PRINCIPLES IN READING. THE FIRST STUDY OUTLINED THE RATIONALE AND PRINCIPLES UNDERLYING THE PROJECT. THE SECOND STUDY INITIATED AND REFINED APPLICATIONS OF REINFORCEMENT PROCEDURES FOR STUDYING EFFECTS OF DISCRIMINATION TRAINING ON READING. STUDY NUMBER THREE DEMONSTRATED THE RELEVANCE OF REINFORCEMENT FOR READING ACQUISITION. THE FOURTH STUDY INVOLVED 4-YEAR-OLD CHILDREN (2 BOYS, 1 GIRL) ENTERING THE CAMPUS LABORATORY SCHOOL. THE CHILDREN USED A RESPONSE REINFORCEMENT APPARATUS WHICH PROVIDED CANDY, PENNIES, OR TOYS AS REWARDS FOR APPROPRIATE RESPONSES ON TWO TYPES OF LANGUAGE DISCRIMINATION TASKS. THE SYSTEM PROVIDED SELF-VARIABLE REINFORCERS. RESULTS DEMONSTRATED THE FEASIBILITY OF USING THE EXPERIMENTAL PROCEDURE FOR LONG PERIODS WITH INDIVIDUAL SUBJECTS. RESULTS AND CONCLUSIONS FROM THE FIRST FOUR EXPERIMENTS WERE THEN USED IN FOUR SEPARATE EXPERIMENTS DESIGNED TO STUDY THE MANNER OF DEVELOPING EVALUATIVE MEANINGS IN READING. THESE EXPERIMENTS IN THE FIFTH STUDY WERE CONDUCTED CONCURRENTLY. EIGHTY STUDENTS IN THE FOURTH AND FIFTH GRADES PARTICIPATED. CHILDREN WERE BROUGHT UNDER EXPERIMENTER CONTROL AND REQUIRED TO RESPOND TO A FORCED CHOICE FORMAT FOR TESTING SEMANTIC DIFFERENTIATION. SUBJECTS WERE REQUIRED TO SELECT SYLLABLES ASSOCIATED WITH 20 POLAR EVALUATIVE TERMS RANDOMLY PRESENTED WITH 12 RANDOMLY INSERTED BUFFER TERMS. CONDITIONING PROCEDURES ESTABLISHED EVALUATIVE MEANINGS IN ALL BUT ONE GROUP. RESULTS OF AN ANALYSIS OF VARIANCE ARE PRESENTED COMPARING SEMANTIC DIFFERENTIAL PERFORMANCE AMONG THE FIVE STUDY EXPERIMENTS. (WN)