Nine cases of salivary duct carcinoma were reviewed clinically, histologically and immunohistochemically, with special evaluation of biomarkers with prognostic significance (p53, Ki67, c-erbB-2 and DNA content). Eight tumours occurred in the parotid gland and one in the submandibular gland. The average age of the patients (8 males and 1 female) was 62.8 years (range = 47-74 years). Tumour size ranged from 1 to 6 cm (mean = 3.46 cm). Recurrences were found in 33.3% (3 patients), regional metastases in 44.4% (4 patients) and systemic metastases in 33.3% (3 patients). Three patients died of their disease (median survival = 12.3 months), one is alive with the disease (follow-up of 222 months) and 5 are alive without evidence of disease (mean follow-up of 75 months). p53 protein nuclear immunostaining was positive in 66.6% and c-erbB-2 overexpression was observed in 100% of the tumours. Ki 67 positivity ranged from 6.75% to 47.5% of tumour cells (mean = 21.3%). DNA aneuploidy was found in 4 tumours (44.4%) and DNA diploidy in 5 (55.5%). Our results seem to indicate that Ki67 immunostaining can be useful in the evaluation of the biological behaviour of these tumours, as well as the presence of a high proliferative index of aneuploid cells and the presence of distant metastases.