Monoclonal antibodies were used to examine the presence and nature of tumor associated macrophages and T-lymphocytes in 26 cases of squamous cell carcinoma of head and neck. The content of macrophages varied according to the differentiation of the carcinoma: high differentiation was evidenced by a labelling index by an index between 13.5% and 23.7%, poor differentiation from 27.4% to 35.8%. T-lymphocytes were found where tumors were inflamed, but there was no significant correlation between tumor differentiation and infiltrating T-lymphocytes. The present results that prognosis decreases with the increasing number of tumor associated macrophages in squamous cell carcinoma.