We report a case of T-cell hairy-cell leukemia with a dual rearrangement of Ig- and T-cell receptor genes. The cytochemical, transmission electron microscopy, and surface antigens data (CD3+, CD8+, CD11+, HLA-DR+, CD19-, CD20-) were consistent with a T-cell hairy-cell leukemia. Molecular analysis according to Southern revealed a dual rearrangement of immunoglobulin heavy-chain (JH) and T-cell receptor beta (TcR beta) chain genes. Our findings suggest that the coexistence of JH and TcR gene rearrangements, frequently detected in acute leukemia, may also be observed in hematologic malignancies derived from more differentiated cells.