The serum concentrations of three separate tumor markers, squamous cell carcinoma antigen (SCC Ag), carcinoembryonic antigen (CEA) and Cyfra 21-1 were clinically correlated in 86 randomly selected patients with squamous cell carcinoma involving the head and neck. Positive findings for each tumor marker were totalled and statistically analysed. The upper limits of normal for SCC Ag, CEA and Cyfra 21-1 were set at 1.5, 2.5 and 2.0 ng/ml, respectively. Positivity rates were 20.6% for SCC Ag, 14.0% for CEA and 41.7% for Cyfra 21-1. Elevated Cyfra 21-1 concentrations correlated somewhat with age, whereas elevated CEA levels correlated with the site of tumor involvement. Overall, Cyfra 21-1 appeared to be the most useful marker in head and neck squamous cell carcinoma.