A renal agent labeled with a 99mTc and quantitatively secreted by the tubules has been sought for many years. To meet this need, a PAH [p-aminohippuric acid] analog (PAHIDA), was synthesized by the coupling of PAH with nitrilotriacetic acid anhydride, using Sn(II) reduction. This yields a stable complex with 99mTc at a pH of 5.8. The purity and stability of the 99mTc complex were established by ITLC [instant thin-layer chromatography] and high performance liquid chromatography (HPLC). Urinary excretions of the 99mTc PAHIDA and 131I hippurate, determined in mice and rats at different time intervals, are similar. The new compound is clearly excreted but its total clearance is lower than that of hippurate as a result of high protein binding. Rat urine analysis by ITLC and HPLC suggests that the agent excreted is similar to the complex administered to the animals. The 99mTc-labeled agent is rapidly excreted in urine with no significant extrarenal pathway, thus providing excellent renal scintigrams in a rabbit model. The 99mTc PAHIDA contains the R-CO-NH-CH2-COOH grouping, analogous to that in hippurate, and consequently may provide the substrate specificity for renal excretion of this new class of agents labeled with 99mTc.