Plasma cell leukemia is considered as the leukemic variant of multiple myeloma. It is a rare entity. There are two forms: a secondary one following a known myeloma, the diagnosis of which is easy, and a primary one arising without a preceding phase of multiple myeloma. The diagnosis of the latter form is more difficult, a differential diagnosis has often to be discussed with other lymphoproliferative diseases. Prognosis is poor. We report 2 cases of secondary plasma cell leukemia diagnosed over ten years, among 59 of multiple myeloma cases. We describe the epidemiologic, clinical, biological and evolutionary characteristics.