A method for transmitting data in a CTI communications system in the 3.sup.rd party configuration, employs a communications system having a plurality of terminals which, for a communication connection between two or more terminals, generates a call which comprises prescribed information about the connection, a TSP and a plurality of clients which are connected to the TSP and communicate with the TSP via a CTI interface. For the purpose of transmitting files or logging data between the clients, the invention proposes transmitting the data for transmission from one of the clients to the TSP via the CTI interface and writing them to a prescribed memory area for the call. These data can be read by the other clients associated with the call, likewise via the CTI interface.