In the paper the author discusses the importance of the so-called “auxiliary” autoantibodies – not included in the diagnostic criteria, but with a relatively high “specificity” (but not necessarily high sensitivity) for certain diseases and additionally correlated with clinical manifestation, disease activity and treatment and also possessing prognostic value. Because we usually observe very characteristic profiles of these antibodies in certain diseases, assessment of these autoantibodies can be a very useful tool in differential diagnosis of the CTDs, especially in not so rare cases, when basic “marker” autoantibody is absent. We take into consideration only those above-mentioned autoantibodies when kits for assessment are available as a commercial package and for other autoantibodies when the technology of preparation of antigens and autoantibody assessment is so simple that the whole procedure can be done in a routine way.