Lymphocytic infiltrate is often present in cervical cancer lesions, possibly reflecting an ongoing, but ineffective, immune response to the tumour. Recently, evidence has accumulated for systemically impaired T-cell functions in cancer patients, associated with decreased expression of signal-transducing zeta (ζ) chain dimer molecules on circulating T-cells and NK-cells. Here, we report on the intralesional downregulation of ζ chain expression on T-cells in cervical carcinoma. Paraffin-embedded or snap-frozen sections from 24 different cervical cancer specimens were studied. Paraffin-embedded tumour-positive (n = 7) and tumour-negative (n = 15) pelvic lymph nodes were also included in the study. Immunostaining was performed on consecutive sections with antibodies specific for CD3-ε or the CD3-associated ζ chain dimer. Antigen retrieval by sodium citrate/microwave treatment was essential for ζ staining of paraffin sections. The amount of ζ positive cells was quantitated and related to the number of CD3-ε+ cells in corresponding tumour areas. Of the 24 cervical cancer specimens studied, ζ chain dimer expression was reduced in seven cases and strongly reduced in the other 17 samples. In tonsil control sections, CD3-ε and CD3-ζ were always co-expressed in almost equal numbers. Also, both tumour-negative and -positive lymph nodes showed ζ chain expression which equalled that of CD3-ε expression. These data indicate that a decreased expression of signal-transducing ζ molecules on tumour-infiltrating T-cells is frequent in cervical cancer. The apparently unimpaired ζ chain expression within draining lymph nodes suggests that local tumour-derived factors at the primary site are instrumental in ζ chain down-regulation.