Human facial appearance plays an important role in medical diagnosis. In medical genetics, pain management, and psychiatry, judgments about the configuration of the face may substantially influence clinical evaluation and treatment. Often these judgments are entirely subjective, based on the observer's experience, skill, and intuition - leading to considerable diagnostic variability. Recent interest in improving objectivity has been driven in part by advances in molecular genetics. Successful application of molecular technology is critically dependent upon accurate clinical diagnosis. Classical anthropometric techniques and related photogrammetry have been used with some success to evaluate facial configuration objectively, but they provide at best limited data about a highly complex surface.