62 consecutive patients with newly diagnosed malignant non-Hodgkin’s lymphoma (NHL) were investigated for the presence, type, and amount of serum and urine monoclonal immunoglobulin abnormalities. The overall incidence of monoclonal gammopathy (MG) was 81%. M components of the IgM and IgG classes were found in the serum of 52% of the patients. Their concentration was below 10 g/l in 54% of cases and above 20 g/l in 26% of cases. The highest incidence of serum M components (75%) was seen in plasmocytoid lymphocytic lymphoma (PLL) and the lowest (38%) in follicular center cell lymphoma. A monoclonal free light chain, i.e., Bence Jones protein (BJP), was documented in the urine of 61 % of cases with a daily excretion comprised between 0.01 and 9.24 g. The isolated urinary excretion of BJP was a major finding accounting for 36% of all MG found in association with NHL. It occurred in all histopathological subtypes with a frequency ranging from 17 % of PLL to 37 % of small lymphocytic lymphoma.