A study of an optical and two stylus-type instruments for measuring surface finish was conducted. The stylus-type instruments are demonstrated to be inaccurate on metals that have a Rockwell hardness less than C-66. The inaccuracy is attributed primarily to surface damage caused by the stylus. The optical instrument causes no surface damage. Stylus-type instruments are proven also to be unsatisfactory for rating relative degree of roughness unless gross roughness differences are considered.