Bell's phenomenon is an important physical sign in clinical medicine. An assessment of Bell's phenomenon may help to explain or localize the cause of ocular disease and lead to the diagnosis of systemic disease. We report in this paper our findings in 508 patients who presented consecutively to a general ophthalmic practice, and who were examined for their Bell's phenomenon and for lagophthalmos. The study demonstrated a good deal of variability not only in the amount but also in the type of Bell's phenomenon response in normal patients. It also demonstrated the usefulness of Bell's phenomenon in specific clinical situations. The literature on the usefulness of Bell's phenomenon is reviewed.