Abstract： Background The YIGSR is a pentapeptide, from the laminin-1 of the β1 chain, which can mediate cell adhesion and bind the 67 kD laminin receptor. The purpose is to evaluate the usefulness of 99mTc-YIGSR, a novel tumour radiotracer, in the receptor imaging of Ehrlich ascites tumour.Methods Using S-Acetly-NH3-MAG3 as chelate, YIGSR, a pentapeptide from laminin, was tagged with 99mTc. 99mTc-YIGSR was detected in the tumour group bearing Ehrlich ascites tumour and blocked group. Tumour, normal, inflammatory and blocked groups were imaged. Results Through reverse phase Sep-Pak C18 chromatogram, it was revealed that YIGSR could conjugate with S-Acetly-NH3-MAG3, and be radiolabelled at room temperature and neutral pH with a radiolabelling yield of 62%, and of 4% without chelate. 99mTc-YIGSR was rapidly cleared from kidney, then liver. The imaging findings showed tumour tissue accumulated initial radioactivity at fifteen minutes after injection in the tumour group, and the uptake increased to peak at three hours with a tumour/muscle ratio (T/M) of 11.36, then cleared slowly to a T/M of 7.50 at eight hours. The tumour uptake of radiotracer in blocked group was significantly lower with T/M of 4.61 at three hours and 0.89 at eight hours. The T/M was only 3.72 at three hours and 1.29 at eight hours after injection in inflammatory group. Compared with inflammatory group and control obstructive group, the ratio of T/M in tumour group was significantly different (P<0.001). Conclusions Using S-Acetly-NH3-MAG3, we radiolabelled YIGSR with 99mTc. 99mTc-YIGSR possesses many merits of tumour imaging: rapid visualization, high sensitivity and specificity, and satisfactory target/nontarget ratio. Our data suggest 99mTc-YIGSR is a promising tumour radiotracer.