The invention relates to tracing of a malicious call to be implemented in a telecommunications network, especially in a mobile communication network. The inventive idea is that the called subscriber activates the tracing service in real time on finding the call to be malicious. One way of activating the tracing service is a service code sent from the called subscriber's terminal equipment and defined by the operator. The means required for implementing the service may be located according to the operator's wishes either in a mobile services switching center or in an intelligent network.