Surgical decompression of the intratemporal facial nerve from the geniculate ganglion to the stylomastoid foramen was carried out in 91 patients with Bell's palsy. All of the patients had denervation exceeding 95%, and a suprastapedial lesion. Edematous swelling of the nerve was assessed using the following three grades: + +, nerve swells beyond the bony facial canal; +, nerve swells beyond the nerve sheath, but within the bony canal, and -, no notable swelling observed. Varying degrees of swelling of the nerve were noted in all of the patients from onset to the end of the ninth week. The incidence of + + swelling was highest within 3 weeks of onset and then declined. + + swelling was most often noted in the vicinity of the geniculate ganglion, and was thought to be a manifestation of inflammation due to herpes simplex virus infection. There was a clear time dependency of the swelling in the horizontal and pyramidal segments, but not in the mastoid segment. After the ninth week, the incidence of swelling decreased sharply and no swelling of the nerve was observed in about one-third of the patients. Considering the etiology and the analysis of edematous swelling, we propose that the course of Bell's palsy be differentiated into an acute phase (the first 3 weeks after onset), a subacute phase (from the fourth to ninth weeks) and a chronic phase (after the tenth week).