Abstract: A method and test apparatus for testing the tooth flank profiles of large diameter gears, contemplates the provision of two contact elements and a measuring feeler, which is movable along a X-axis parallel to the connection line of both contact elements and a Y-axis extending transversely thereto. The contact elements are inserted into a respective tooth gap or space of a gear which is to be measured and the test apparatus is brought into a position where both of the axes are located in a plane normal to the gear axis. Then, there is determined the origin of a X-Y-coordinate system formed by both axis, the measuring feeler thereafter is moved along at least one tooth flank and the thus measured coordinates are compared with reference values. Importantly, the invention contemplates measuring the spacing between both of the contact elements and determining therefrom the spacing of the coordinate origin from the gear axis.