Squamous-cell carcinoma of the head and neck includes a heterogeneous group of tumours of the upper air and food passages for which prognosis is difficult to assess. In fact, patients in comparable stages may have diverse clinical courses and responses to similar treatments. In order to better define the prognosis of each patient there is therefore a need to identify novel biological markers which reflect more accurately growth rate, progression and metastatic potential of each tumour. We assessed whether metastases correlate with microvessel counts (i.e. intratumoral vascularity) using the CD-31 monoclonal antibody (MAb) and p53 mutant protein expression, determined in the primary by immunocytochemical methods in 70 patients with locally advanced head and neck cancer. Patients were treated with concurrent chemo-radiotherapy; 50 of these presented loco-regional node metastasis at diagnosis whereas 3 cases, initially node-negative, developed distant metastasis during the period of observation. No feature was predictive for objective response to treatment. The overall mean and median blood vessel density at "hot spots" was 37.42 and 36, respectively, and 57% of the tumours expressed p53 mutant proteins. These 2 biological markers were significantly associated. Patients with metastases (loco-regional and distant) had a significantly higher mean blood-vessel density than those without tumour spread. Also, patients with p53-positive (+/++) tumours had a significantly higher incidence of metastasis than those with negative ones. Multivariate analysis showed that both vascularity and stage, but not p53 expression, are significant and independent predictors of metastasis in this series.