Five, 3-month-old mongrel dogs weighing between 4.5 to 5.5 kg were studied to evaluate and compare the efficiency of Tc-DTPA, Tc-MAG , and Tc-DMSA in detecting gentamicin-induced renal tubular injury. After baseline renograms using all three methods, all dogs received daily intramuscular injections of gentamicin at a dose of 30-45 mg/kg. Additional studies were obtained after a cumulative dose of 450, 1,575, and 2,250 mg of gentamicin was reached. Glomerular filtration rate (GFR), effective renal plasma flow (ERPF), and percentage of total renal uptake measurements were calculated. Baseline and post-gentamicin injection blood urea nitrogen (BUN) and serum creatinine values were determined. A Duncan test revealed significant renal function impairment at 450 mgs of cumulated gentamicin with Tc-DMSA and at 1,575 mgs of cumulated gentamicin for Tc-DTPA and Tc-MAG . There was no correlation between BUN and serum creatinine values when compared to gentamicin (p > 0.05). The images obtained with Tc-MAG were of better quality than those obtained with Tc-DTPA even under severe renal dysfunction. Percentage of Tc-DMSA uptake indicated renal damage, before than GFR and ERPF. BUN and serum creatinine measurements were poor indicators of gentamicin-induced renal failure. 99m 99m 99m 99m 99m 99m 99m 99m 99m 3 3 3