SummaryFifteen patients with locally far advanced, nonpretreated head and neck squamous cell carcinoma were treated with low-dose recombinant interleukin- 2, using 10 daily perilymphatic injections. The therapy was well tolerated. No tumor regression was observed. Tumor biopsies were taken before and after treatment. Histopathological studies including evaluation of the mononuclear cell infiltrate and immunohistochemical detection of human leukocyte antigen (HLA) expression on tumor cells were performed. HLA class I was not detectable in 1 of 10 samples, and HLA class II expression was seen in 2 of 10 samples. As compared to pretreatment biopsies, no changes were found after treatment. This is in agreement with the lack of a clinical response.