We describe the histopathology, immunophenotype and immunogenotype of 10 cases of peripheral T-cell lymphoma. The majority of patients showed disseminated disease at the time of diagnosis. From a histopathological view point the cases were classified into 5 types: T zone lymphoma (4 cases); Lennert lymphoma (2 cases); pleomorphic lymphoma, small all type (2 cases); pleomorphic lymphoma of medium-sized cell type (1 case); pleomorphic lymphoma of large cell type (1 case). In most of them the neoplastic cells demonstrated a mature T-cell phenotype: CD3+, CD4+, CD8-, CD43+, CD45RO+, CD45RA-, CD20- and surface immunoglobulins. All cases studied displayed gene rearrangements for the T-cell receptor beta chain while the immunoglobulins genes remained in germinal configuration. Antibodies against the human T-cell lymphotropic virus type I were not found in the 9 samples studied.