THE NATURE OF COMPREHENSION IS DEFINED AND CLARIFIED. THE LITERATURE IS SURVEYED TO SHOW THAT THE DEVELOPMENT OF CONCEPTS IS IMPORTANT IN INTELLECTUAL ACTIVITIES. IT IS POINTED OUT THAT CONCEPTS ARE BUILT FROM PERCEPTS, IMAGES, SENSATION, AND MEMORIES, AND THAT THE STEPS WHICH ARE EMPLOYED AS CONCEPTS ARE BUILT AND REFINED AND INCLUDE PERCEIVING, ABSTRACTING, AND FORMING GENERALIZATIONS. A MODEL INCLUDING PERCEPTION, APPERCEPTION, ABSTRACTION, APPRAISAL, IDEATION, AND APPLICATION IS PRESENTED TO EXPLAIN THE INTELLECTUAL PROCESSES. REFERENCES ARE INCLUDED. THIS PAPER WAS PRESENTED AT THE ANNUAL CONFERENCE AND COURSE ON READING (22D, UNIVERSITY OF PITTSBURGH, JULY5-15, 1966), AND PUBLISHED IN A REPORT OF THAT MEETING, "PROGRESS AND PROMISE IN READING INSTRUCTION," BY THE SCHOOL OF EDUCATION, UNIVERSITY OF PITTSBURGH, PITTSBURGH, PENNSYLVANIA 15213. (BK)