Federalism as a system of government seem to have been more generally accepted as the best system of government for managing multi-ethnic states in order to allow each of the constituent units enough elbow room for autonomous development Though the system has been in operation for centuries now, there is a large measure of disagreement among scholars on the theory of federalism This disagreement has led use of terms as quasi federalism to describe some countries whose brand of federalism seem different from the American type, despite the fact that they are apparently practicing a federal system. This paper explicates on the theory of federalism extensively and the present trends in both its theory and practice. It relies on the theory of intergovernmental relations as an explanatory variable. Its data is mainly from secondary sources. It concludes that since different countries that adopt the federal principle, are different in many respects there are bound to be noticeable differences in these different systems.