Previously we evaluated new methods to localize the source of bacteriuria in monkeys with experimental urinary tract infection. A high level of diagnostic accuracy was obtained with studies of antibody coating of urinary bacteria by immunofluorescence, 131iodine hippuran quantitative scintillation camera studies with the patient in the hydropenic state and 67gallium citrate scintiphotos. We identified unique patterns that differentiated cystitis, ureteritis, pyelonephritis and renal or perinephric abscess. Herein we review our clinical experience with these combined techniques in 40 patients and correlate the degree of accuracy of these studies with that of standard radiographic examinations. In 20 patients diagnostic studies also were compared to the findings of split ureteral urine cultures or bacteriologic culture of renal tissue obtained from surgical specimens or autopsy. The use of the quantitative scintillation camera studies done with the patient in a state of controlled hydropenia increased clearly the level of diagnostic sensitivity in demonstrating the source of a urinary tract infection compared to urine culture and excretory urography alone. In patients with an abnormal 131iodine hippuran study the performance of 67gallium renal imaging on the same day usually provided information that allowed specific localization of the source and extent of an infection. Both studies must be performed with a high degree of resolution over the renal areas and then must be interpreted carefully to ensure accuracy. Study of antibody coating of urinary bacteria was helpful in suggesting the presence or absence of upper urinary tract disease but was less sensitive and accurate than the combined radionuclide studies.