After pointing out the disadvantages of the commonly used methods for recursive identification of multi-input, multi-output systems, the paper discusses the recursive identification of multi-input, multi-output systems, using a normalized input-output description in terms of polynomial matrices straightforwardly related to a canonical state space realization. The identification procedure involves two steps: (1) identification of a set of invariant indices, (2) parameteric identification. The results which can be obtained with various techniques are evaluated comparatively on a simulation example and on a real plant, a distillation column from Naphtachimie.