The paper considers the conditions under which a system of dynamic equations will be corisisterrt with some prespecified inultivariate equilibrium specification. Connections are also drawn between recer► t develuprnents in the analysis of multivariate error correction models and the theory of co-integration and what is kr► uwn as —rhe Internal Model Principle" in the design of robust linear feedback rules . Apart from clarifying and generalising our understanding of error currectiun systems and co-- integration this approach suggests a relatively simple method for identifying the restrictions that detern-iir,e whether a given dynamic system satisfies the conditions for being an error correction specification.