Method for performing the testing of the correct operation of the secondary radar transponder of an aircraft moving in an area covered by a secondary air traffic surveillance radar, characterized in that it has: - a first step which implements: - an operation of measurement of the power transmitted by the transponder, from the measurement of the power received from the transponder in reply to each interrogation transmitted by the radar; - an operation of measurement of the local average rate of reply of the transponder to the interrogations transmitted by the radar, performed by counting the number of interrogations for which the radar has received a reply originating from the transponder; the first step being performed while the operating parameters of the radar are not modified relative to the operation parameters; - a second step which implements an operation of measurement of the sensitivity of the transponder, performed by transmitting additional interrogations with transmission power levels increasing or decreasing over time, and by determining the transmitted power level in the transmission of the first interrogation below which the transponder does not transmit a reply; the second step being performed by modifying the operating parameters of the radar so that the additional interrogations required for the measurement can be performed, during the time interval following the last operational interrogation during which the aircraft remains located in the main Sum channel lobe of the antenna of the radar, with a transmitted power in the direction of the transponder framing the sensitivity threshold of the transponder; - a third step which implements an operation of measurement of the maximum rate of reply that the transponder can sustain during a short time interval of given duration, the operation being performed by transmitting a plurality of additional interrogations and by counting the interrogations for which the transponder has transmitted replies; the third step being performed by modifying the operating parameters of the radar so as to make it possible to transmit, during the time interval following the last operational interrogation during which the aircraft remains located within the main Sum channel lobe of the antenna of the radar, a number of successive interrogations that is sufficient to cause an absence of reply from the transponder. - a first step which implements: - an operation of measurement of the power transmitted by the transponder, from the measurement of the power received from the transponder in reply to each interrogation transmitted by the radar; - an operation of measurement of the local average rate of reply of the transponder to the interrogations transmitted by the radar, performed by counting the number of interrogations for which the radar has received a reply originating from the transponder; the first step being performed while the operating parameters of the radar are not modified relative to the operation parameters; - a second step which implements an operation of measurement of the sensitivity of the transponder, performed by transmitting additional interrogations with transmission power levels increasing or decreasing over time, and by determining the transmitted power level in the transmission of the first interrogation below which the transponder does not transmit a reply; the second step being performed by modifying the operating parameters of the radar so that the additional interrogations required for the measurement can be performed, during the time interval following the last operational interrogation during which the aircraft remains located in the main Sum channel lobe of the antenna of the radar, with a transmitted power in the direction of the transponder framing the sensitivity threshold of the transponder; - a third step which implements an operation of measurement of the maximum rate of reply that the transponder can sustain during a short time interval of given duration, the operation being performed by transmitting a plurality of additional interrogations and by counting the interrogations for which the transponder has transmitted replies; the third step being performed by modifying the operating parameters of the radar so as to make it possible to transmit, during the time interval following the last operational interrogation during which the aircraft remains located within the main Sum channel lobe of the antenna of the radar, a number of successive interrogations that is sufficient to cause an absence of reply from the transponder.