[en] Most commonly used infection imaging agents are specific for inflammation. Some newer agents like labeled antimicrobials and peptides have shown infection seeking properties. Research is underway for synthesis of newer imaging agents specific for infections. In this quest we have labeled and bio evaluated /sup 99m/Tc-ceftriaxone. Ceftriaxone is a commonly used third generation cephalosporin antibiotic having a broad anti-bacterial spectrum but has more specificity for gram-negative bacteria. /sup 99m/Tc-ceftriaxone was prepared at ph 7 by adding 30 mg of ligand to /sup 99m/Tc in the presence of 50 mu g of SnCl/sub 2/./sup 2/H/sub 2/O. Boiling for ten minutes gave maximum labeling yield (96+1.76%). The stability at room temperature both with and without human serum was more than 90% till 24 hours. In-vitro binding revealed maximum binding of 68% and 47% with E.coli and S.aureus respectively after 4 hours incubation. Biodistribution studies in normal rats showed maximum uptake in hepatobiliary system followed by kidney. In infection and inflammation models the maximum target to non- target ratios of 12.66 +- 2.59, 2.36 +- 0.30 and 1.44 +- 0.53 were achieved with E. coli, S. aureus and oil inflammation respectively 4 hours post injection. Scintigraphic findings also correlated with biodistribution results. (Orig./A.B.)