The permanent headquarters of the World Health Organizatio, in Geneva, is recognised as one of the major works of Jean Tschumi, who won the international competition in 1960. Shaped by the imposing linear block housing the Secretariat and the Conference Hall at lower level, the ensemble displays a highly individual plastic expression that profits remarkably from the technical solutions used. From the spectacular pre-stressed concrete frame structure, to the conception of the aluminium and glass envelopes animated by a subtle, slanted brise-soleil, the incorporation of some very smart – and decidedly novel – technology assists in the architectural definition of the international body's remarkable European home. As the specialist press at the time was keen to emphasise, the latest technical gadgetry featured prominently in Tschumi's design. The technology assumes a particular interest not only because of its complexity, but also because of the close relations established with constructional elements. This interaction deserves to be explored; this paper will propose a reading of the material aspects of this group of buildings centred on the notion of integrated building engineering systems, a notion of major importance that is all too often overlooked.