Familial Mediterranean fever is characterised by recurrent and self limited attacks of fever and polyserositis and its devastating complication is the development of renal amyloidosis. In order to detect the presence of early glomerular and tubular damage in patients with familial Mediterranean fever and to assess the possible role of beta 2-microglobulin in the inflammatory attacks of this disease, serum and urine beta 2-microglobulin concentrations and microalbuminuria were evaluated in these patients. A total of 20 patients with familial Mediterranean fever were studied on and off colchicine treatment; seven of these patients developed a familial Mediterranean fever attack when they were off treatment. During the familial Mediterranean fever attacks serum beta 2-microglobulin concentrations decreased, whereas fractional excretion of beta 2-microglobulin, urine beta 2-microglobulin creatinine, and urine albumin/creatinine ratios increased. We conclude that glomerular and tubular functions deteriorate during the attacks. Further studies are needed to discover the effector(s) causing these transient glomerular and tubular disorders.