We analysed TCR-γδ expression in tumour-infiltrating lymphocytes (TIL) obtained from 13 patients with colorectal cancer and simultaneously isolated the T lymphocytes from normal intestinal tissue (IL) to compare the frequencies of TCR-γδ expression in TIL, IL. and peripheral blood lymphocytes (PBL) in the same patient. Flow cytometric analysis showed that the frequency of TCR-γδ expression in TIL (275 ± 1·84%) was significantly lower than that in IL (15·28 ± 9·45%, P < 001). However, a larger quantity of TIL was separated than IL per unit weight of specimen, so the total number of γδ T cells obtained per unit weight was not different between tumour tissue and normal intestine. In addition, phenotypic analysis revealed that about half of the TCR-γδ TIL were CD8+ (CD4+, 3·0 ± 3·1%; CD8+, 54·7 ± 19·9%, mean ± s.d. of five patients), and a very similar result was obtained in TCR-γδ+ IL (CD4+ 2·7 ± 2·4%; CD8+, 53·1 ± 17·4%). In contrast, most TCR-γδ+ PBL were double-negative (CD4+. 3·2 ± 3·0%; CD8+ 20·6 ±7·4%). These results indicated that TCR-γδ+ CD8+ T cells selectively and consistently localized in colorectal tumour tissue, similarly to normal intestinal epithelium.