The validity of introducing reading on the preschool level is the premise behind this study. The objective was to determine the effectiveness of the Categorical Sound System (CSS) developed by the author, as a highly structured linguistic-based readiness and beginning reading program, on kindergarten children from underprivileged and privileged populations. The latter group was further divided into those in private kindergartens and those in public school. CSS is a simplified and accelerated readiness and beginning reading program designed to take the child from reading readiness to the 2.7 grade level. Four hundred and five kindergarten pupils took part in the study for which the major hypothesis stated that the introduction of a formalized and highly structured individualized reading readiness and beginning reading program on the kindergarten level would be more effective in developing basic prereading and early reading skills than a less formal routine kindergarten program for all groups tested at all ability levels. Control and experimental groups were used, with both receiving pretests and post-tests. The hypothesis proved to be valid for all groups tested. Tables, a bibliography, and samples of the prereading check and the teacher's rating scale are included. (NH)