Method and device for radar transmission and reception by dynamic change of polarization notably for the implementation of interleaved radar modes are provided. A radar transmission-reception method and a device for implementing this method, the method alternatively implementing two modes of operation, a short range mode exploiting short pulses and a long range mode exploiting modulated long pulses, the method consisting, for each mode, in: producing two synchronous radiofrequency (RF) transmission signals having between them a phase-shift θ of controllable given value; radiating two radiofrequency waves, each corresponding to one of the transmission RF signals produced, by means of two colocated radiating sources each having a given polarization axis; handling the reception of the backscattered radiofrequency signals picked up by each of the radiating sources, and delivering two radiofrequency (RF) reception signals each corresponding to a radiofrequency signal picked up by one of the radiating sources, a phase-shift θ′ being applied between the two signals delivered, θ′ being able to be determined as being equal to θ.