The aim of this study was to prepare Tc-99m-Sulfamethoxazole complex and evaluate its efficiency as an infection imaging agent. The Sulfamethoxazole was labeled with Tc-99m and its biological efficacy as a potential radio tracer for Staphylococcus aureus infection was investigated in bacterially infected Albino Wistar rats. The radiolabeling yield was found to be 95 +/- 3.07% and remained constant at more than 93 +/- 0.1% even in serum for 240 min after radiolabeling. Tc-99m-Sulfamethoxazole prepared with high yield localized well in the bacterially infected muscle of the rats. Tc-99m-Sulfamethoxazole may be developed as a radiopharmaceutical agent to distinguish infection from inflammation by nuclear imaging.