With HMPAO we have synthesized in our laboratory, we labelled 99mTc to canine leukocytes. Experimental abscess made by subcutaneous injection with Staphylococcus aureus was imaged with these 99mTc 1abelled leukocytes. Labelling efficiency of HMPAO with 99mTc was 66.2%.+- 14.6% (N=9). Labelling efficieney of leukocytes with 99mTc-HMPAO was 54% +- 7.79 (N=7). CelI bound radio activity in 99mTc-HMPAO labelled leukocytes was around 80%. when these cells were incubated in plasma in vitro at 37`C for 5 hours. In vivo cell bound activity was over 80% at 24 hours after injection. One day and four days after inoculation, uptake at the inflammatory focus was found with 99mTc labelted leukocytes. Uptake showed up in 4 hour image, and the uptake at the lesion was most prominent in 24 hour image. These findings show that in-house-synthesized HMPAO could be used for labelling leukocytes with 99mTc, and that 99mTc-HMPAO-labelled leukocytes were so stable and viable that inflammatory focus could be visualized with these 99mTc-labelled leukocytes.