We investigated the in vitro stimulation of peripheral blood lymphocytes with tumor extracts and serum-derived fractions from five patients with laryngeal carcinomas. Lymphocyte cultures were propagated by Interleukin-2 or phytohemagglutinin. Sera of the same patients were fractionated and the amount of circulating immune complexes present was measured by a Raji cell assay. A positive lymphocyte reaction was found in only two of the five cases after stimulation with autologous tumor extract. This response was determined by an increased 3H-thymidine incorporation. The reactive lymphocytes could be restimulated by autologous serum-derived fractions, which contained high or very low levels of circulating immune complexes. A characterization of different lymphocyte subsets revealed an elimination of natural killer cells and a relative enrichment of T-helper cells during in vitro stimulation and cultivation.