Background: Syndecan-1, a transmemebrane heparan-sulfate glycoprotein, is predominantly expressed by plasma cells and is readily shed and released under certain pathologic conditions and remains biologically active to plasma cells behaviour. Aim of the work: To assess the level of syndecan-1 in relation to lupus nephritis (LN) and systemic lupus erythematosus (SLE) activity. Patients and methods: The study included 60 SLE patients subgrouped according to the presence of LN and activity. SLE disease activity index (SLEDAI) was assessed. Serum syndecan-1 level was measured. Results: The patients mean age was 25.9 ± 8.6 years, they were 54 females and 6 males with a disease duration of 3.8 ± 3.4 years. There was a significant difference in the level of syndecan-1 between healthy control (46.3 ± 12.2 ng/ml) and SLE patients whether they were with active LN (150.2 ± 31.1 ng/ml) (p