We tried to apply the avidin chasing system to the inflammation-seeking scintigraphy using radiolabeled nonspecific polyclonal IgG. We studied the pharmacokinetics of technetium-99m and iodine-125-labeled biotinylated murine polyclonal IgG followed by an avidin chase injection in model mice with inflammatory foci. Avidin chase decreased the circulating radioactivity of 99mTc and 125I, which was a major problem for inflammation-seeking scintigraphy using radiolabeled nonspecific polyclonal IgG, to 9.3% and 19.3% of that without an avidin chase injection, respectively. Inflammation-seeking scintigraphy with the aforementioned method would be better than that with conventional method.