A semiautomatic procedure to calibrate a robot manipulator for improving positioning accuracy is proposed. An error-correcting transformation is estimated using the point-pairs in the theoretical and actual coordinate frames. The theoretical points are obtained using a 3D model of the inspected part, whereas the actual points are derived with image processing and analytic geometry techniques. The estimation of the error-correcting transformation is based on a leastsquare method. Experimental results are described to illustrate the calibration procedure.