The T-cell receptor beta-chain variable (TCRBV) region repertoire expressed by tumor-infiltrating lymphocytes was characterized by immunohistochemical analysis using a panel of 18 monoclonal antibodies on cryosectioned specimens of 14 primary vertical growth phase (VGP) melanomas with a T-cell infiltrate histopathologically defined as brisk or nonbrisk. T lymphocytes present in the VGP of all patients displayed a restricted T-cell receptor usage, with a pattern of reactivity similar in brisk versus nonbrisk infiltrates. No evidence of restriction was found in the extra-VGP lymphocytic infiltrates, when available, within the same specimen. Furthermore, the repertoire of TCRBV expressed in nodal metastases was similar to that of the corresponding primary melanomas in the two cases tested. The results obtained by this in situ analysis indicate that the TCRBV repertoire in VGP is determined by a preferential migration of T lymphocytes, possibly indicative of an immune response to melanoma-associated antigens.