The present study was conducted to evaluate radioimmunoimaging (RII) and in vivo distribution of mixedantibodies 99mTc-EGFR-mAb and 99mTc-CD44- mAb in nude mice bearing human lung adenocarcinoma xenografts.Single and mixed applications of the two radiolabeled monoclonal antibodies (mAbs) were compared. Directlabeling of 99mTc was applied to radiolabel the EGFR and CD44 mAbs. The properties of the radiolabeledantibodies were then characterized. RII and assessment of the distribution of the antibodies in nude mice bearinglung adenocarcinoma xenografts were achieved by applying separate and combined doses of 99mTc-EGFR-mAband 99mTc-CD44-mAb. The labeling rates of 99mTc for EGFR-mAb and CD44-mAb were 91.5% ± 3.8% and 92.3%± 4.1% respectively, with specific activities of 2.8 and 2.9 MBq/μg, respectively, and radiochemical purities (RCP)of 96.5% and 96.2%. The radioactivity uptake of the combined application of both radiolabeled antibodieswas clearly higher than with a single application of either alone. The relative values of target-to-nontarget (T/NT) measured through the regional interest (ROI) technique were 5.59 ± 0.42 (mixed antibodies), 2.78 ± 0.20(99mTc-EGFR-mAb), and 2.28 ± 0.16 (99mTc-CD44-mAb) in the RII. The body distribution of the radiolabeledantibodies and their imaging results were basically identical. Application of the mixed antibodies with 99mTc-EGFR-mAb and 99mTc-CD44-mAb can increase the radioactivity uptake of tumor tissue, leading to more idealtarget-to-nontarget ratios, and therefore superior results.