The invention relates to a system for identification of an electronic label 100, with interrogation without contact, by an information exchange unit in proximity to which the label to be interrogated is arranged, in which: - the electronic label has no power supply of its own and comprises means forming an antenna 101, rectifier means 106, 107, receiver and decoder means 112-115, an information memory 125, and responder means, and - the exchange unit comprises means forming an antenna, transmitter means and receiver means.; According to the invention, the antenna-forming means of the electronic label consist of a single antenna, and the terminals of this antenna are directly and simultaneously linked: . to a rectifier circuit 106, 107 making it possible to derive the DC voltage for supply of the internal circuits of the electronic label, . to a demodulator circuit 112, 113, 114 making it possible to derive the coded interrogation signal, and . to a circuit with controllable, variable impedance 117. Moreover, the receiver means of the exchange unit comprise means for detecting the disturbances in the electromagnetic field resulting from the variations in impedance of the variable-impedance circuit and for deriving therefrom the response signal produced and transmitted by the electronic label.