The association of monoclonal gammopathy (MG) with B-cell non-Hodgkin's lymphomas (NHL) is a well known phenomenon. The aim of the present work was to study the incidence, type of monoclonal component and prognostic significance of MG in a population of 255 cases with B-cell NHL. Among 255 evaluable patients with B-cell NHL, 145 were males and 110 females with a median age of 58 years (range 18-85). There were 166 patients with the various subtypes of aggressive (intermediate/high grade) NHL and 89 with the various subtypes of low risk. MG was detected in 44 patients (17.2%) with a median age of 61 years (range 23-79). There were 22 cases (8.6%) with IgG type (IgG/(k) 15, IgG/(lambda) 7), 4 cases (1.6%) with (IgA/(k) 3, IgA/(lambda) 1) and 18 cases (7.0%) with IgM (IgM/(k) 12 IgM/(lambda) 6). MG was found in 15.6% of the patients with aggressive NHL, while in low risk NHL the incidence was 20.2% (N.S.). The type of MG according to histological classification was as follows: Aggressive NHL: IgG 17 cases, IgA 2 cases, IgM 7 cases: low risk NHL: IgG 5 cases, IgA 2 cases, IgM 11 cases. The distribution of MG according to stage of the disease was as follows: stage I (4.5%), stage II (18%), stage III (6.8%) and stage IV (70.4%). The median survival of patients with aggressive NHL with MG was 17 months compared to 40 months of those without (P=0.22). Similarly the median survival of patients with low risk NHL and MG was 51.5 months compared to 38.5 months of those without (P=0.90). In conclusion MG was detected in 17.2% of cases with B-cell NHL. IgG-MG was more frequent in cases with aggressive NHL, while IgM in cases with low risk NHL. MG was mostly associated with advanced stage and had not any prognostic significance on survival.