Until now the error description of CMMs has been carried out assuming rigid body kinematics. This paper resents a method for describing the error structure of the CMM including both the non rigid body effects and the thermal induced effects. Individual error parameters are described by special polynomial fitting procedures. A final set of parameters can he generated from the measured quantities of the CMM by a special computer program. Using these parameters, a small error correction program has been developed, which has been applied to a suitable 3CMM. Results of this work will be presented.