A technique is presented for the calibration of robots based on a maximum-likelihood approach for the identification of geometrical errors. A new experimental setup is presented for measurement of the end-reflector position errors. The errors of position and orientation of the measuring device are included in the algorithm and identified. Tests have been carried out on a robot with six degrees of freedom. Tests show that this technique can reduce the mean error distance by a factor of more than 15. Compensation algorithms are presented, based on the improved knowledge of the geometrical model.>