Two male infants aged 6 months presented with Escherichia coli septicaemia and urinary tract infection. Despite seemingly appropriate antibiotic therapy, a swinging fever, painful enlargement of both kidneys, sterile leukocyturia and renal failure persisted. Excretory urography, ultrasound scan, computerized tomography and magnetic resonance imaging showed diffuse infiltrative disease. 99mTc dimercaptosuccinic acid uptake was minimal, but a 67Ga-citrate scan showed striking diffuse uptake by both kidneys suggestive of inflammatory cell infiltration. Bilateral renal parenchymal malakoplakia was diagnosed on tissue examination. Bilateral parenchymal involvement of the kidneys by this chronic granulomatous disease has not previously been reported in infancy and is fatal if untreated. The lesion is believed infection-induced, due to defective bacterial activity of the macrophages, possibly related to an abnormally low cGMP/cAMP ratio. Treatment with intracellularly active trimethoprim-sulphamethoxazole, rifampicin and ascorbic acid resulted in complete recovery of the one infant so treated over a period of months.