Swedish children, who receive extensive readiness activities in their first months in school, are taught through a diagnostic approach which involves observation, diagnosis, and treatment of difficulty by the classroom teacher. Results of a 6-year longitudinal study of the system revealed (1) the degree of success achieved by a program of remedial instruction coupled with the regular curriculum and (2) the reliability of reading readiness test batteries and perception tests for measuring reading readiness. Classes were divided into experimental and control groups, with the experimental groups receiving remedial instruction from a special teacher. The differences between the two groups were studied by, among other methods, analysis of covariance. Subtest scores of readiness tests were found to be significant contributors to analysis of readiness. The readiness variable was found to have the highest prognostic value of all measures considered. And the combination of early diagnosis and remedial instruction was found to have a positive effect on the children involved. Tables of results and explanations of their meanings are included. (MD)