In this study, we aimed to evaluate renal tubular function in familial Mediterranean fever (FMF). Urinary N-acetyl-beta-D glucosaminidase (U-NAG, beta2-microglobulin (U-beta2M) and microalbumin (Ua) levels were measured in children with different clinical stages of FMF (58 patients with FMF, 9 patients with amyloidosis secondary to (FMF). Control groups were healthy children (n=21), children with upper respiratory tract infection (URTI) (n=21) and with steroid sensitive nephrotic syndrome (SSNS) (n=18). U-NAG was significantly increased in patients with a recent diagnosis of FMF compared to patients with FMF on colchicine and to healthy controls. In patients with recently diagnosed FMF, a marked decrease in U-NAG, U-beta2M and Ua were determined after three months on colchicine therapy. On the other hand, U-NAG and Ubeta2M levels were increased in patients with FMF during attacks and then decreased in the post-attack period. U-beta2M in patients with FMF during attacks was significantly different from patients with URTI. Finally, U-NAG and U-beta2M were increased significantly in patients with FMF-amyloidosis and SSNS when compared with other FMF groups and healthy controls, respectively. In conclusion, the high U-NAG value in newly diagnosed patients compared to that of patients taking colchicine and the decline of U-NAG and U-beta2M levels after attack to the levels observed in colchicine users (without a significant change in Ua value) suggest that the renal injury early in the course of FMF might be dominantly at the level of the tubuli.