Previous studies have suggested that alterations of the p53 gene are the most common genetic abnormality in human cancer. The aims of the present study were to evaluate p53 protein (p53P) immunostaining in adenoid cystic carcinoma (ACC) of the salivary gland and to correlate the expression with patient survival. A total of 27 cases of ACC in the parotid gland (n = 12) and the minor palatine glands (n = 15) were studied, with ten cases each of normal parotid and palatine glands as non-neoplastic controls. Staining was performed with mouse monoclonal antibody DO-7 against p53 (Dako, USA) using the ABC method. Stained nuclei irrespective of intensity or frequency were considered as positive. The frequency of positive nuclei was evaluated as the p53P index (p53PI), the percentage of the total nuclei in the reference epithelium. Clinical survival data were available for patients for periods up to 156 months. Our data showed that no normal tissues showed immunoreactivity with p53P in their nuclei. Thirteen of 15 (87%) cases of palatal and two of 12 (17%) cases of parotid neoplasms stained with p53P and the p53PI ranged from 0.01 to 10%. The number of p53P positive tumors was significantly higher in palatal than in parotid neoplasms, suggesting that palatal ACCs may be more aggressive in comparison with parotid ACCs. Our data also showed that the number of p53P positive tumors was significantly increased in patients who died of tumors than in patients with no evidence of disease at the end of the follow-up period between 60 to 156 months. These results suggest that p53P may be involved in the development of salivary gland ACCs and that p53P analysis may be a useful indicator of poor prognosis.