Renal cell carcinomas (RCC) contain tumour infiltrating lymphocytes (TIL) but these are essentially immunosuppressed in that they do not generate effective antitumour immune responses in vivo. These TIL comprise predominantly alpha beta T cells, although gamma delta T cells are also present. The repertoire of gamma delta T cells in RCC, however, has not been fully investigated. To identify the gamma delta T cell populations infiltrating RCC, this study has characterised the gamma delta T cell receptor (TCR) repertoire expression in these tumours and compared this to autologous normal kidney and autologous peripheral blood. A semi-quantitative reverse transcriptase/polymerase chain reaction technique was used for amplification of rearranged TCR V-C mRNA transcripts. Primers specific for the four human TCR V gamma and six V delta subfamilies were used, each in conjunction with a primer specific for either the C gamma or C delta region. The specificity of the PCR products was confirmed by Southern blotting and hybridisation with an internal C region probe. A densitometry score was assigned to each DNA band and the level of V gene expression was determined as ratio of C delta gene expression. The gamma delta TCR expression in each sample was determined as a ratio of C delta: glyceraldehyde phosphate dehydrogenase densitometry score. This demonstrated that TCR C delta gene expression was significantly higher in RCC compared to normal kidney (P < 0.019), suggesting a selective infiltration of gamma delta T cells into the tumour. Furthermore, we observed differences in the TCR V gamma and V delta repertoires between RCC and peripheral blood. V gamma l expression was significantly decreased (P < 0.043) whereas there was an over-representation of V gamma 4 transcripts (P < 0.028) in RCC compared to blood. A significant reduction in expression of both V delta 1 (P < 0.028) and V delta 3 (P < 0.051) was also observed within kidney tumour compared to peripheral blood. These findings show that expression of the gamma delta TCR repertoire in RCC differs from that in peripheral blood and normal kidney.