Abstract: A method of measuring errors in the rotational truth of gear teeth of a gear by means of a measuring device having a feeler guide which is pivotable about a pivot axis parallel to the gear axis, the feeler guide guiding a feeler which is prebiased in the direction of the gear and cyclically engages into the gear teeth as the gear rotates. The feeler together with the feeler guide is pivotable about its pivot axis and can be displaced back in relation to the feeler guide. An electronic circuit determines the largest degree of rearward displacement of the feeler during each measuring cycle in that it stores signals delivered by the feeler and compares such stored signals with one another. During each measuring cycle there is formed from a number of signals delivered by the feeler as well as from a number of subsequently delivered signals a respective mean value.