During the past few years there have been several changes in the educational system of Ontario: a reorganization of the Department of Education, the abolition of the school section, the establishment of post-secondary institutions of applied arts and technology, and the reform of Grade 13. Others are in prospect: the abolition of Grade 13 departmental examinations, the requirement that all elementary school teachers must have a university degree, and the establishment of an educational television network. These changes are evolutionary rather than revolutionary. Representing less a break with tradition than a logical expansion of it, they are developments that are consistent with the rationale of the system as it has evolved in the course of one hundred and fifty years.This study is concerned with the nature and significance of these changes in relation to the dimensions and organization of the system itself. It describes the system as it exists today, identifies those features of it which are either unique or distinctive, and explains by reference to their historical development how these unusual features have come to occupy their present position. The author also investigates the disadvantages as well as the advantages of the present approach to education in Ontario, pointing out that the system has become such a vast complex that it is exposed to the dangers of fragmentation and compartmentalization. The basic problem is one of co-ordination, which could be remedied by closer liaison between government departments and by the establishment of improved communications between educational institutions.This account is a valuable contribution to the public debate on education in Ontario.