Objective To investigate the clinical and pathological characteristics of renal involvement in Beh(c)et's disease (BD).Methods A retrospective analysis was carried out in BD patients complicated with renal damage who were admitted to Peking Union Medical College Hospital from June 1998 to July 2012.Results Twenty patients with renal involvement constituted 3.2％ of all the 618 hospitalized BD patients.The presentation of renal disease was chronic glomerulonephritis in 6 patients (1 with nephrotic syndrome),renal tubular acidosis in 1 patient,renal artery stenosis in 7 patients,renal vein thrombosis in 1 patient,and chronic renal failure of unknown etiology in 5 patients.Kidney biopsy was performed in 5 patients,3 of them revealed glomerular minor lesion,mild mesangial proliferative glomerulonephritis and chronic tubularinterstitial nephropathy,respectively.The other 2 patients underwent a second biopsy,one with glomerular minor lesion transforming into IgA nephropathy of grade Ⅲ on Lee's glomerular grading system after 6 years,and the other with IgA nephropathy of grade Ⅱ progressing to grade Ⅳ after 2 years.After the diagnosis of renal BD,one patient with uremia underwent peritoneal dialysis,while the remaining 19 patients received immunosuppressant (or with combination of glucocorticoid,angiotensin converting enzyme inhibitors and angiotensin Ⅱ receptor blockers.etc.) therapy.Among the 8 patients with renal vascular involvement,2 underwent surgery,and several received anticoagulant therapy.During the follow-up of 13 patients,the urine protein quantifications were reduced,and renal functions remained relatively stable.Conclusion Renal damage is relatively uncommon in BD patients.There are various clinical spectrums for renal BD.Routine screening with urinalysis,serum creatinine and imaging studies should be carried out for the early diagnosis of renal BD.