Tc-99m gluceptate renal imaging was compared with the intravenous urogram in 41 patients. While the specificity of the examination was essentially the same for both techniques, the sensitivity for the detection of renal mass lesions was better with gluceptate imaging. The study suggests the desirability of a shift in emphasis from the IVU to the Tc-99m gluceptate scintigram in the early evaluation of suspected renal mass lesions, and merits further clinical evaluation.