The study is aimed at current view of significance of evaluation of serum immunoglobulin free light chain levels in different types of monoclonal gammapathies according to clinical practice needs. In the beginning, current technical means and pitfalls of the examination of monoclonal immunoglobulins and their structural components in serum and/or urine were evaluated. Methodical and interpretative aspects of a new established automated immunochemical method are described more deeply. It enables quantitative evaluation of serum free light chains (S-FLC) with high sensitivity and specificity. Significant benefit of the evaluation of both S-FLC levels and kappa/lambda ratio, particularly for the diagnosis of Bence-Jones, non-secretory and IgD multiple myeloma, is emphasized in this paper. It is also important for the continuous evaluation of the progression of the disease, response to treatment, and stable “plateau” achievement, early detection of the progression or relapse of the disease as well as treatment resistance in all types of multiple myeloma. The attention is also paid to the importance of the examination of S-FLC for the diagnosis and evaluation of the treatment of primary systemic AL-amyloidosis, primary macroglobulinaemia as well as less common types of MG (solitary plasmocytoma, B-type non-Hodgkin’s lymphoma, light-chain deposition disease). Issues of monoclonal gammapathy of undetermined significance were also mentioned. It can be claimed that examination of the serum FLC, kappa/lamda ratio and theirs changes significantly extend spectrum of standard parameters using for the diagnosis and evaluation of the outcome of several types of monoclonal gammapaties treatment.

        Key words: immunogloblulin free light chains, automated immunochemical analysis, Bence-Jones myeloma, nonsecretory myeloma, AL-amyloidosis, primary macroglobulinaemia, monoclonal gammapathy of undetermined significance, diagnosis, therapy