Method and system for performance monitoring of distributed applications. A sensor intercepts every request of service for a server that is generated on a client. If the request meets a filtering condition (for example, defined by the address of the server, the web page from which the request is originated and/or the selected link) the measuring of a corresponding transaction on the client is enabled; at the same time, the request is updated by inserting a correlator. The request is then transmitted to the server. If the request includes the correlator, the measuring of a sub-transaction originating from the request is also enabled on the server. The parameters measured on the client and on the server are then associated with the correlator.