Keratinocyte-derived interleukin-7 (IL-) is a potent growth factor for some cutaneous T-cell lymphomas (CTCL). We investigated the expression of IL-7 receptor (IL-7R) in several types of cutaneous and nodal lymphomas. We studied 44 CTCL (13 mycosis fungoides, six Sézary syndromes, eight pleomorphic small cell, and 17 pleomorphic medium and large cell), 10 lymphomatoid papulosis (LP), five cutaneous B-cell lymphomas, and five reactive lymphocytic infiltrates. Twenty nodal T-cell lymphomas, and three reactive lymph nodes were also analysed. Frozen sections were stained with monoclonal antibodies directed against IL-7R, CD25, CD30 and T antigens (CD3, CD2, CD5, CD7, CD4, CD8), using the alkaline phosphatase-antialkaline phosphatase technique. No expression of IL-7R was observed in cutaneous B-cell lymphomas, benign cutaneous lymphoid infiltrates, and reactive lymph nodes. IL-7R was expressed by more than 20% of lymphoid cells in 50-75% of all histological subtypes of CTCL, and by more than 50% of cells in 15-50%. IL-7R was expressed by more than 20% and 50% of cells in 40% and 10% of nodal large T-cell lymphomas, respectively. Eighty-nine per cent of CTCL and LP expressing IL7-R also expressed CD25+, compared with 58% of IL-7R--CTCL and LP (P < 0.05). No association of IL7-R and CD30 expression was found. In conclusion, CTCL frequently express IL-7R. This expression is not related to the epidermotropic characteristic of the infiltrate. In CTCL and LP, IL-7R expression is associated to CD25 expression, but not to CD30 expression.