A prospective, controlled, double-blind study was designed to evaluate the effect of steroid treatment on the natural history of Bell's palsy. Fifty-one patients were included in the study between 1972 and 1974. The patients were evaluated and started on treatment within two days of onset of Bell's palsy and followed for six months. Treatment was given in randomized double-blind fashion and consisted of either vitamins or a total of 410 mg of prednisone plus vitamins in descending doses over 10 days. The recovery of facial motor function was determined by three physicians who had no knowledge of the treatment received by the patients. They examined photographs of the patients taken six months after onset of paralysis in eight positions of facial function and categorized them as to complete fair, or poor recovery of facial function. These results of this evaluation were submitted to the biostatistician who broke the treatment code. The results of this study demonstrate no statistically significant beneficial effect of steroid therapy upon recovery from Bell's palsy. Factors considered included the patients' age, sex, the presence of pain, ageusia, hyperacusis, diabetes, hypertension, the progression and degree of palsy, the results of nerve excitability and salivary flow tests, and the time at which recovery was first noted or became complete. Bell's palsy remains without a proven efficacious treatment.