The presence of fibrillation in mimic muscles in Bell's palsy was investigated during a clinical and electrophysiological follow-up study. Fibrillation was present in 58,82% of the frontalis and mentalis, but only in 29,41% of the orbicularis oculi (OO) muscles tested. Furthermore, the amount and the time course of fibrillation were also different, without any significant differences concerning the EMG pattern among the three muscles. The compound muscle action potential (CMAP) of the OO was negatively correlated with the presence of fibrillation. The recovery of OO was slightly better than that of the others muscles. An attempt of interpretation of these findings is made on the line of a possible sparing of the OO nerve fibers and the unique histochemical properties of the OO. On these grounds, fibrillation in the OO in Bell's palsy is less frequent than as in the other mimic muscles, and its absence is not necessarily indicating a good prognosis.