The invention relates to a method for measuring and analyzing the performance of a control circuit in an industrial process. Different parameters (indices) illustrating the state of the control circuit are combined in an intelligent manner such that each combination of index (VI, IAE, CTI, OI) values represents a specific example state of the control circuit. The indices and combinations of their values are selected in advance on the basis of expert knowledge and process research. A momentary state of the control circuit is deduced by computing the performance indices on the basis of the measurement data illustrating the control loop operation and by examining which (one) of the predetermined index value combinations best correlate(s) with the corresponding reference combination values. The reference state representing the best correlating combinations is then deduced to be the momentary state of the control circuit.
