OBJECTIVES: To analyze the incidence of facial nerve dysfunction following parotidectomy and to correlate this with the extent of parotid gland resection, the pathological diagnosis, and the clinical setting. DESIGN: A review of prospectively collected data from a dedicated computerized head and neck database. SETTING: Tertiary care center. PATIENTS: Between 1987 and 1995, 248 patients underwent 259 parotidectomies performed by the same surgeon (C.J.O'B.). Indications were clinical tumor (n=213) or sialadenitis (n=46). There were 235 previously untreated patients and 13 who had undergone a prior operation on that side. Facial nerve function was normal in 242 patients and abnormal before surgery in 6. Cancers accounted for 88 parotidectomies and benign disease accounted for 171. Of 213 clinical tumors, 41 (19%) were situated deep to the plane of the facial nerve. RESULTS: The facial nerve was intentionally sacrificed in 28 of 259 operations (18 total and 10 partial sacrifice). In 230 parotidectomies in which facial nerve function was normal before surgery and the nerve was preserved, the incidence of initial postoperative facial weakness was 29%. Based on the diagnosis and extent of surgery, rates of facial weakness were 16.5% and 13%, respectively, for benign and malignant tumors located in the superficial lobe and treated with limited superficial parotidectomy; 30% and 34% for sialadenitis treated with complete superficial parotidectomy and near-total parotidectomy, respectively; 31% and 100%, respectively, for benign and malignant lobe tumors treated with near-total parotidectomy; 83% for parotidectomy associated with a neck dissection; and 33% for patients who had previous parotid surgery. Permanent weakness occurred in 13 (5.6%) of 230 patients, but 10 of these 13 had simultaneous neck dissection and facial nerve dysfunction involved only the marginal mandibular branch. Recovery of normal facial movements occurred within 6 months in 46 (68%) of 67 of those with initial weakness. CONCLUSIONS: The likelihood of temporary facial weakness correlated with the extent of surgery and was especially influenced by tumor location deep to the plane of the facial nerve, previous parotid surgery, a diagnosis of sialadenitis, and the addition of neck dissection to the parotidectomy. Permanent weakness mainly affected the marginal mandibular branch when neck dissection was included.