Histological features and prognosis of patients with mucoepidermoid carcinoma of the parotid gland were analysed. Tumours from 13 patients were classified according to histological grades and immunoreactivity for HEK-2/neu. Surgical resection of the tumour was performed for all patients, and the overall five-year survival rate was 69 per cent. The patients whose histological grades were 1 or 2 showed a 100 per cent five-year survival rate, but no patient with grade 3 survived five years. Also, patients who had tumours that overexpressed HER-2/new had a lower survival rate (25 per cent) than patients with tumours that had weaker immunostaining (89 per cent). We considered tumours classified as grade 3 plus strong HER-2/neu expression to be ‘high malignancy’, and compared them with ‘low malignancy’ tumours that were grade 1 or 2 and had weaker HER-2/new staining. Patients with high malignancy tumours had shorter recurrence-free intervals and shorter overall survival than patients with low malignancy tumours. The overall survival period of the low malignancy cases was much longer than the recurrence-free interval; unlike that in the high malignancy tumour patients. These results suggest that the combination of histological grades and expression of HER-2/neu may be a useful predictor of the prognosis for mucoepidermoid carcinomata.