This study describes and tests the aptitude treatment interaction (ATI) approach to reading. The rationale which forms the basis of ATI--pairing student to method--evolved from the works of Piaget and other psychologists whose studies focus on the general, and cognitive, development of children. From these studies, it was determined that readiness, primarily maturation and past learning, was the dominant factor in deciding the method most appropriate for the student. In the present study, the Metropolitan Readiness Test was administered to kindergarten classes in the spring of 1973. Students in the treatment group received instruction in accordance with ATI placement procedures. Those in the control group received basal reading instruction without regard to their readiness levels. At the end of two years, there was a significant difference in favor of the treatment group on the reading subtest of the Iowa Tests. This was interpreted as validation for the theoretical model underlying the ATI approach to reading. (Author/AA)