Background Osteopontin(OPN)is one kind of cytokine which can play a number of roles in promoting activation of T lymphocyte,regulating balance between Th1 and Th2,participating in cell-induced immunologic response and stimulating B lymphocyte to express multi-clone antibodies.Some researches have showed that OPN may be involved in the pathogenesis of systemic lupus erythematosus (SLE).The aim of this study was to investigate possible association of a single nucleotide polymorphism (SNP) at position 9250 in exon 7 of the OPN gene (OPN gene 9250) with SLE in Chinese patients.Methods Totally 158 patients (18 males and 140 females) fulfilled the revised criteria for SLE by the American College of Rheumatology in 1982 and 180 healthy volunteer controls (34 males and 146 females),all from the south of China,consented to participate in the study.OPN gene 9250 polymorphism was detected by polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP).Results The frequency of TT genotype of the OPN gene 9250 was significantly lower (52.5% vs 70%,P