Ankylosing spondylitis (AS) can be accompanied by extraarticular manifestations in the cardiovascular, pulmonary, neurologic and renal organs. Secondary renal amyloidosis is the most common cause of renal involvement in AS (62%) followed by IgA nephropathy (30%), mesangioproliferative glomerulonephritis (5%) as well as rarely membranous nephropathy (1%), focal segmental glomerulosclerosis (1%) and focal proliferative glomeruleonephritis (1%). Treatment associated nephrotoxicity may result from non-steroidal anti-inflammatory drugs or disease modifying agents. The purpose of this paper was to alert for the possibility of renal damage in AS and to analyse the frequencies of different etiologies of renal involvement. Two typical case reports of renal involvement in AS are presented to illustrate the clinical course of such patients. Renal side effects and possible pre-existing renal diseases should be taken into account while choosing the appropriate medication for patients with AS.