The aim of the study is to characterize the expression pattern of galectin-3 (Gal-3) in renal tissues of patients with systemic lupus erythematosus (SLE) nephritis and to determine whether tissue and serum Gal-3 are associated with SLE nephritis. Gal-3 expressions were examined with immunohistochemistry in renal biopsy specimens of 88 patients with SLE nephritis and in five normal specimens. Activity and chronicity indexes and glomerular Gal-3 expressions were analysed in each specimen. Serum Gal-3 levels were measured using enzyme-linked immunosorbent assays in 20 patients with SLE, including 11 with nephritis, and in 50 healthy controls. Glomerular Gal-3 expression was observed in 81.8% (72/88) of patients with SLE nephritis but not in 5 controls. Gal-3 staining was attributed mainly to its cellular expression rather than its deposition, and Gal-3 expression levels were correlated with histologic activity indexes, anti-dsDNA titers, and complement 3 and 4 levels. Serum Gal-3 levels were higher in patients with SLE, particularly in those with nephritis, than in healthy controls, and correlated with anti-dsDNA titers. In conclusion, glomerular Gal-3 expression in renal tissue and serum Gal-3 levels were elevated in patients with SLE nephritis versus healthy controls; moreover, they reflected disease activity. These findings suggest that Gal-3 might contribute to the inflammatory process in SLE.