Background & Objective: Bell ’ s palsy (BP) is a relatively common disease characterized^�by the sudden onset of facial paralysis. In this disease, the facial muscle is paralyzed and the patient cannot close the eye or control the saliva in the involved side._�The incidence rate of this disease in the world is between 11.5-40.2 cases per 100,000. The cause of this disease is yet to be found. This study is an attempt to investigate the demographic. Characteristics of these patients as well as the environmental factors involved in this disease in Ardabil.

 Methods: In this cross-sectional study which was cauducted in Ardabil province during a 2-year period (2001-2003) all the patients referring to neurology clinics were evaluated by a questionuaire in terms of demographic features and whether they were affected by the disease.

 Results: 140 cases (out of 6550) were affected by Bell ’ s palsy. The incidence rate was high among 20-30 year-olds (17.85%) and was equal among females and males. Incidence of BP was higher in cold seasons. A high incidence was also observed among farmers, who sweat abundantly due to their job nature.

 Conclusions: The results are consistent with hypotheses regarding viral etiologies [e.g., reactivation of herpes simplex] of Bell ’ s palsy and it can be activated by cold exposure. The results also indicated that the disease is more prevalent in cold seasons.