The article is focused on the issue of circular interpolation and positioning accuracy measurement on five axis CNC machine tools. Measurement of circular interpolation accuracy was realized in one plane (XZ) and more planes (XY,YZ,XZ), positioning accuracy was measured in one axis direction. NC program modifications for each measurement on machine tools were carried out. The main characteristic of the paper is measuring system and principle of measurement of positioning by laser interferometer and circular interpolation measurement by ballbar.