Abstract The measuring accuracy of coordinate measuring machines (CMMs) depends to a large extent on the software system implemented. For this reason, the Physikalisch-Technische Bundesantalt (PTB) supported by the Commission of the European Communities (Community Bureau of Reference; BCR) has started a project to test this software. Simulated data sets representing parts of geometric elements with known distortions were distributed to manufacturers of CMM software. The results of various software packages were compared with those of PTB's reference software. All evaluations were based on the Gaussian least-squares method. The main result of the test showed that only 37% of the solutions were acceptable. An investigation was also conducted into the ability of current CMM software to measure gears and to check geometric tolerances according to ISO 1101 and ISO 5459.