In the last two years the authors have noted the cases of five patients with pulmonary tuberculosis to which intermittent treatment with Rifampicin was administered (twice weekly, 600-900 mg/day), in association with Ethambutol. Between 2 and 6 months after the treatment was started, 24-72 hours after the last administration of Rifampicin acute renal failure developed in all five cases. Two of the patients also had signs of liver failure (increased serum transaminase, lowered pseudo-cholinesterase, increased BSP retention), and in one of them there was also a hematological syndrome consisting in hemolytic anemia and thrombocytopenia. Four of the patients benefited from application of diuretics, hydroelectrolytic re-equilibration and/or hemodialysis. One of the subjects died 12 hours after being hospitalized, with acute pulmonary oedema, refractory to treatment. From the histopathological viewpoint glomerular lesions were found in the kidney (non-uniform thickening of the basal membranes by PAS-positive deposits). In two of the patients various immunological tests have been carried out (Coombs test, lymphocyte-migration inhibition, serum and urine immunelectrophoresis) that, by their alterations, provide some elements indicating the immunological origin of the phenomena.