We report three cases of malignant T cell lymphoma of peripheral T lymphocyte origin. This morphological entity was first described by Lennert and Waldron. The diagnosis based on morphological criteria only is difficult because of the many lymphoid malignancies. Immunological characterization is necessary for the identification of the proliferative T lymphocyte subset with a panel of T monoclonal antibodies. Correlations were established between immunological phenotype and clinical and evolutive aspects which are particularly varied in T lymphoproliferative disorders.