The drive to 'unify' post-compulsory education and training systems is one of the most important current developments in education policy. However the concept of 'unification' lacks clarity, is not widely recognised, and is pursued through different measures in different countries. In this paper we propose a conceptual framework with which to analyse the different meanings of and debates about unification. Using England and Scotland as examples, we show how the framework may be used to analyse existing systems, reform strategies, and (...) processes and pressures for change. The framework is exploratory and will need to be tested and developed in relation to a wider variety of education systems. (shrink)