Background and Objectives: Adenoid cystic carcinoma (ACC), the most common malignant tumor of submandibular and minor salivary glands, is characterized by a high rate of local recurrence and distant hematogenous metastasis and tendency to invade peripheral nerves. In spite of radiotherapy and surgical treatment, the long-term prognosis is dismal. Today, many studies are being conducted using the immunohistochemical markers to help in the evaluation of ACC prognosis. The present investigation was performed to survey immunohistochemically HER2/neu over expression in adenoid cystic carcinoma of salivary glands. Materials and Methods: The 24 existing samples of formalin-fixed paraffin embedded specimen were stained with HER2/neu markers. Tumors with moderate (2+) to strong (3+) complete membrane staining in at least 10% of the tumor cells were scored as positive for over expression. Results: The overall frequency of over expression for HER2/neu was 45.8% and 11 specimen were positive for HER2/neu expression. A significant relationship was found between HER2/neu over expression and grade of ACC. No significant relationship was detected between immunostaining of HER2/neu and histologic pattern. Conclusion: HER2/neu immunostaining might be reliable and useful for evaluation of ACC prognosis.