An optical heterodyne profilometer breadboard with surface roughness measurement sensitivity to 0.1 A has been developed and demonstrated. Optical and electronic common-mode rejection techniques were employed in the optical heterodyne precision phase measurement scheme to resolve the optical phase to one part in thirty thousand. Vibration-induced optical phase jitter in the system was nearly eliminated by these common-mode rejection techniques. This noncontact profilometer is capable of characterizing mirror surfaces and is not limited only to flat and/or highly reflective surfaces. Con-cave surfaces, such as the x-ray mirrors for the Advanced X-ray Astrophysical Facility (AXAF), may be characterized as well. Several mirror samples, including two x-ray mirror samples, have been characterized with the optical heterodyne profilometer. Roughness measurement results for the x-ray mirror samples have been compared with those obtained by other methods.