Between 1985 and 1987 102 children, age 0-14 years, presented with a first acute symptomatic E. coli urinary tract infection. Investigations included early 99mtechnetium dimercaptosuccinic acid (DMSA) scan (which was performed at a median of 27 days), ultrasonography, micturating cysto-urethrography and indirect voiding radionuclide cystography using 99mTc DTPA. Follow-up DMSA scan was carried out after 6 months. Twenty-one of 102 of initial DMSA studies showed diminished uptake of radionuclide and 12 showed cortical scarring. Twenty-nine patients had significant vesicoureteral reflux (VUR). The finding of diminished uptake on the initial scan was significantly associated with fever, systemic upset, length of symptoms and a peripheral blood leucocytosis, (p less than 0.05). In addition the finding was associated with fever and loin pain in the older child. Both diminished uptake and scarring were more common in refluxing kidney units. We propose that, in children with UTI, diminished uptake on early DMSA scan localises infection in the renal parenchyma.