In seven human adenocarcinomas and a non-neoplastic granulomatous disease of the lung, gamma delta+ infiltrating lymphocytes (TIL) could be isolated and selectively expanded in vitro upon culture in interleukin-2 (IL-2), without any additional stimuli, indicating a prior activation in vivo. In most cases gamma delta TIL were predominantly V delta 1+, despite a normal V delta 2:V delta 1 ratio in paired peripheral blood lymphocytes, suggesting a possible expansion of this subset in response to localized antigens/superantigens. Moreover, in five patients it was possible to identify a V delta 1- V delta 2- TIL population which by polymerase chain reaction (PCR) analysis was shown to be heterogeneous as V delta gene usage, inclusive of V delta 3,4,5,6,7 and 8. Of note, these V delta regions have not been found in peripheral blood so far. Finally, in all cases, gamma delta TIL displayed killing activity of the autologous tumour, which appeared to be more restricted in the case of V delta 1+ cells. Altogether, these findings suggest a preferential expansion, at the tumour site, of V delta 1+ cells and of cells expressing V delta genes other than V delta 2.