Clinical, immunological, immunophenotypical, pathological and molecular biological studies were performed on tumor infiltrating lymphocytes (TIL) and lymph node lymphocytes (LN-ly) of 8 patients with squamous cell carcinoma of the oral cavity and oropharynx treated with 10 daily locoregional injections of low doses of IL-2 before surgery. No complications were seen during or after surgery. In 3 cases the LN-ly showed a moderate LAK activity, higher in the LN-ly omolateral to the tumor and near the IL-2 injection site; in 2 of these 3 patients a good LAK activity was induced after 6-day culture with IL-2. The LN-ly derived from nodes next to the tumor showed a decreased NK activity and proliferative ability both in basal conditions and after in vitro lymphokine challenging. LN-ly of 2 IL-2 treated patients showed high levels of mRNA encoding for IL-2-R, while it was absent in 2 untreated cases. Immunophenotypical studies on TIL showed statistically improved levels of CD25+ and LAK1+ cells in treated cases. Clusters of CD11c+ (macrophages) cells were seen close to the neoplastic sheets.