The present work consists a research on rationality in the organizations. In this direction, it follows the studies on substantive organizations. Ours aims was the transition of instrumental rationality to communicative rationality, in case of a psychiatric hospital. For in such a way, the movement of psychiatric institutional reform was approached. The epistemological orientation of this movement gives consistency to the idea that the recent transformations in these organizations occur in direction of communicative rationality. In the empirical part of this work, the participant observation was used. The results of the research had pointed the communicative rationality as the main rational orientation in organization investigated, what it corroborated the hypothesis of work initially consisting.