Peripheral blood mononuclear cells from a single donor were depleted of T cell receptor (TcR) α/β T cells, stimulated with allogeneic cells, and γ/δ T lymphocyte clones (TLC) were isolated by limiting dilution. Five TLC were cytotoxic against B‐lymphoblastoid cell lines from the stimulating cell donor, and demonstrated a restricted allospecificity in panel cell studies. One of these, γ/δ TLC RNG‐135, was studied in more detail. Its phenotype was CD3+ TcR α/β− TcR γ/δ+ BB3− δTCS1+ CD4− CD8−. Inhibition experiments using monoclonal antibodies indicated that the cytotoxicity of TLC RNG‐135 was mediated through the TcR γ/δ, and directed against an HLA‐DQ molecule. In extended panel cell experiments, this γ/δ TLC only lysed cells carrying the DQA1*0501 and DQB1*0301 genes, either in cis position (on the DR5, DQw7 haplotype), or in trans position (the donor of the stimulating cells, DR3,4; DQw2, w7). Thus, it appears that γ/δ T cells may recognize a particular HLA‐DQ α/β heterodimer, which may be encoded by DQA1 and B1 genes both in cis and trans position. Copyright © 1990 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim