The notes of 158 patients who had undergone surgery of the parotid gland for benign and malignant disease were studied to discover the circumstances in which the facial nerve might be injured. Limited surgery carried as great a risk of injury to the facial nerve as during extended surgery. Extended surgery provided greater risk of injury to the facial nerve on secondary exploration (71 per cent) than on primary exploration (6-5 per cent). It is concluded that every primary exploratory procedure of the parotid gland should be a formal conservative parotidectomy unless the tumour is obviously malignant.