The case history of a patient developing tubulointerstitial nephritis (TIN) during carbamazepine therapy is described. After withdrawal of the drug and introduction of prednisone renal function normalised. TIN is a rare side-effect of carbamazepine of which only a few cases have been described. There seems to be a remarkable time interval of 2 months between the onset of therapy with carbamazepine and the development of TIN.