In Systemic Lupus Erythematosus (SLE) patients, renal involvement is the most important complication during the disease course and directly effects the prognosis of the disease. Its presence and especially histologic type modulates the treatment protocol. It is very important to know the presence and severity of renal lesions in SLE cases both for physician ad patient but the cold face of biopsy and fear is more important for patients than physicians. Hence, it has been thought that without using invasive methods as biopsy, some biochemical parameters in urine might also give a clue about the severity and presence of the renal involvement. In this study, we tried to show that whether the value of glycosamino glycans (GAG), a major element of connective tissue, in urine would be a reasonable test to show the presence and severity of renal lesions. The excretion of GAG found to be higher in 65 patients than 17 control group (p