Abstract: A method and system for controlling the retransmission of data packets which monitors the successive progression of cycles of round trips of message signal transmissions between a transmitter and at least one receiver for avoiding unnecessary retransmissions of data packets which are detected as incorrect during the transmission of sequentially numbered data packets of a data file. Data representative of the progress of cycles are included in the data fields of message signals transmitted to communication devices. Another copy of a data packet is not retransmitted pursuant to a request for retransmission unless the data values related to cycle progression indicate that the last transmitted copy of the data packet was not in transit to the communication device requesting the retransmission at the time the device issued the request.