Impaired cell-mediated immunity has been consistently associated with head and neck squamous carcinoma (HNSC). Previous work has implicated monocytes in this impairment. The present study shows that in a subgroup of untreated patients with advanced HNSC, monocytes are responsible for impaired in vitro lymphokine (leukocyte migration inhibitory factor) production. In view of recent studies suggesting interactions between lymphokines and monocytes in the immune response, the present findings may be relevant to future immunotherapeutic approaches.