Upper urinary tract (renal) infections have been reported to be frequent and difficult to treat in patients with autosomal dominant polycystic kidney disease. This study examined renal infections and responses to therapy in this patient population. Fifteen cyst infections and 11 parenchymal infections occurred during the study. Eighty-seven percent of the cyst and 91 percent of the parenchymal infections occurred in women. Gram-negative enterics were the causative organisms in 92 percent of the cyst and 100 percent of the parenchymal infections. All of the parenchymal but only one of the cyst infections responded to therapy with ampicillin and an aminoglycoside despite favorable sensitivities. Eighty-three percent of the cyst infections were eradicated with use of lipid-soluble antibiotics. It is concluded that Cyst infections are refractory to therapy with the antibiotics commonly used to treat urinary infections; Female preference and enteric organism predominance suggest that these renal infections are acquired retrograde from the urinary bladder.