Electroneuronographic study of the spontaneous course of Bell's palsy shows that chance of a satisfactory spontaneous return of facial function is reduced by 50% when 95% or more maximal degeneration is reached within two weeks of onset. For this reason immediate surgical decompression (including the meatal foramen) was performed on 14 patients with 90% or more degeneration within three weeks of palsy onset. These patients and 13 who refused treatment under similar conditions were reviewed one to three years later by three physicians familial with facial nerve problems. Results show that to obtain satisfactory (80% to 100%) return of facial movements in all cases of Bell's palsy, surgical decompression should be performed within 24 hours when degeneration reaches 90% to 94% within one to 21 days after onset. By using these guidelines, the number of unnecessary operations will be kept under 16%.