Cefoperazone was used in the treatment of infections in 13 cases of chronic renal failure. In 8 cases recurrent urinary tract infections were diagnosed, septicaemia in 3 cases, pneumonia in 2. Cefoperazone 2-4 g daily was a very effective and well tolerated drug. Only one therapeutic failure was noted in a patient with mixed urinary tract infection (strains of Enterobacter cloacae and Klebsiella pneumoniae). No side effects developed, and in patients in the phase of moderate renal failure some decrease of serum creatinine was noted after the completion of treatment.