The author gives a working-definition of a horizontal organisation: an organisation that structurally promotes conditions for equality of power and controls in a function way the ever present tendencies to 'verticalisation'. In the presented model delegation of power is given in the concept of 'areas of relative autonomy' for the various subsystems of the organisation. Participation in the 'area of joint interests' is given in the concept of an 'entente' in which no one has the structural power to enforce his will upon any other one. Decision-making thus is the result of a process of influencing, negociating and deliberating, within limits of time and supplies. Such a horizontal organisation is partly motivated by the ideological needs of the workers in the service, but also by the need to be consistent with the chosen philosophy of treatment. Redefinition and redistribution of responsbilities and competencies is thought to be functional among the contributing disciplines as well as in the working-relation between 'professional' and 'client'. A global description is given of the various practical forms and procedures that proceeded from the above mentioned principle. The author emphasis the importante of an even, up-to-date and wellaimed distribution of information for a real participation in decision making. Organisation-technology is not hostile but helpful to a horizontal organisation. Finally, emphasis is laid on the necessity of the development of a system of 'inner controls' that replaces the more traditional hierarchical authority and a proposal is made for developing such controls.