In this paper, we examine through a multidisciplinary approach – at the crossroad of discourse analysis, semiotics and cognitive psychology – text-figure relations in technical communication. These relations are firstly analysed by means of the inner structure of each mode of expression, privileging an approach inspired by the semiotics. Emphasis is placed on examining perceivable realizations – in the figure, in the text and in the document – which make the text and the figure complementary or even indissolubly linked in the construction of the message. Hypotheses formulated in this way are tested through an experimental evaluation involving users of technical documents. This step, in accordance with cognitive psychology and ergonomics methods, confirms that text and figure, sometimes cooperating, sometimes competing in the expression of technical message, become equal partners in its interpretation.