The aim of this study was to analyze circulating levels of anti-monomeric CRP autoantibodies (anti-mCRP) in serum samples from SLE patients in relation to biochemical and clinical disease activity markers and to identify significant associations be,tween the presence of these an¬tibodies and the relevant clinical manifestations of SLE. Serum levels of IgG anti-mCRP antibodies were detected by enzyme linked immunosorbent assay (ELISA) for sixty patients diagnosed as SLE and met the revised ACR criteria and 30 matched healthy subjects as a control group. Disease activity was evaluated according to the Systemic Lupus Erythematosus Disease Activity Index(SLEDA1) score. Association of anti-mCRP reactivity with clinical features, with other auto-antibodies and with serum concentrations of C3. C4, C1q and CRP were assessed. In this study IgG antibodies to mCRP Were found in sera from 65% SLE, patients compared to 3.3% healthy controls. In SLE patients positive for IgG anti-mCRP antibodies, there were significantly greater frequency of renal affection (76.9% vs 28.5%, P