The aim of the study was to investigate the prevalence of antinuclear and associated antibodies (anti-dsDNA, anticardiolipin, anti-RNP, anti-Sm, anti-SSA and anti-SSB) and/or combinations thereof in systemic lupus erythematosus (SLE) patients with respect to their diagnostic and pathogenetic significance. The prevalence of anti-dsDNA antibodies was strongly influenced by the selection criteria of the patient; the lowest prevalence was found in SLE patients with central nervous system (CNS) involvement; the highest prevalence in patients with nephritis. The results were also influenced by the different assays. Combinding different assays (Farr/PEG ratio) quantitative as well as qualitative differences could be shown between patients with nephritis (Farr/PEG ratio≥5) and with CNS involvement (Farr/PEG ratio<5). No difference in anticardiolipin antibody prevalence between the different SLE patient groups could be demonstrated. Regarding antibodies against RNP, Sm, SSA and SSB, the prevalence was found to be strongly influenced by the criteria used for patient selection. Only in CNS patients and association with anti-RNP and anti-SSB antibodies alone or in combination was found. In pleuropericarditis a weak association with RNP antibodies existed. In conclusion: studying the prevalence and possible pathogenetic significance of antibodies one should always consider patient selection criteria and the effect of the different assays used when analysing the results.