Recent classifications of non-Hodgkin's lymphomas based on combination of morphologic, immunophenotypic, and cytogenetic criteria have individualized mantle cell lymphoma (MCL). This clinico-biological entity which accounts for 3 to 10% of all non-Hodgkin's lymphomas, now appears to be a biological and therapeutic model for the understanding and treatment of hematologic malignancies. The present study consisting of two cases of MCL collated at laboratory of hematology of Rabat Ibn Sina hospital. The morphological appearance of MCL is characterized by diffuse or nodular lymph infiltration in the mantle zone, the osteo-medullary biopsy shows an interstitial infringement characterized by the presence of lymphocytes resembling centrocytes with cleaved and angular nuclei, dispersed chromatin, inconspicuous nucleoli and scanty cytoplasm. The flow cytometry showed immunophenotype positive for surface Ig, CD19, CD20, CD22, CD79b, CD5 and cyclin D1, and negative for CD10, CD23 and CD25. In conclusion, the methods of diagnosis and prognosis evaluation of mantle cell lymphoma are based on the nodular, medullary and blood morphology, the immunophenotypic, cytogenetic and molecular study of neoplastic cells.