From July 1992 to December 2000, 288 cases of monoclonal gammapathy (MG) were collected at the university hospital of Sfax. The middle age of the patients at the time of the diagnosis was 62 years and 7 months with extremes to 18 months and 99 years and median to 64 years. One hundred and eighty-two patients were men and 106 women. Among the 270 observations for which aetiology has been established, 73 were classified MG of undetermined significance (MGUS), 160 myeloma (or plasmocytoma) and 37 other malignant MG (Waldenstrom's macroglobulinemia: 13, lymphoma: 9, alpha heavy chains disease: 6, primary amyloidosis: 5, chronic lymphocytic leukaemia: 4). Rheumatological affections (19.2%), infections and renal failure (10% each), haematological and autoimmune diseases (9.6% each) were pathologies most often associated with MGUS. Agarose gel electrophoresis did not show a monoclonal peak in 16% of the cases. In the 242 patients with a peak on electrophoresis, the peak was in the beta zone in 22% of cases and in the gamma zone in 78% of cases. The IgG isotype represents more than the half of the cases of our set (51.7%). IgG is even more predominant in the MGUS group (65.8%). The IgA isotype counts for 20.8% of the cases in our set and the free light chains (kappa or lambda) for 13.6% of the cases whereas the IgM represents 8.7% only of the 288 cases of our set which involves three cases of IgD myeloma and six cases of biclonal gammapathy.