To investigate the relation between the clinicopathological findings, and the survival of patients with malignant tumours of the maxillary sinus, and the tumour's biological parameters, we examined the expression of p53 and bcl-2 and the number of silver-stainable nucleolar organizer regions (AgNORs) in 23 paraffin-embedded specimens from primary tumours. Fifteen of 23 (65 per cent) maxillary tumours expressed p53 and two of 23 (nine per cent) tumours expressed the bcl-2 gene product. The mean number of AgNORs per nucleus was 5.2 +/- 2.4. There was no relationship between the expression of p53 or bcl-2 and the patient's clinical course. In contrast, there was a statistically significant difference in the survival of patients with a high (> 6) number of AgNORs and patients with a low (< 6) number of AgNORs. These data suggest that the number of AgNORs may be useful in evaluating the prognosis of patients with malignant maxillary sinus tumours.