Abstract: 99mTc-HYNIC--Ala-BBN(7-14)NH2 was prepared by choosing Tricine and EDDA as coligands, and the in vitro stability and biodistribution were compared for these two compounds. ITLC and HPLC analyses showed that the labeling yield of both compounds was more than 95%, and the radiochemical purity (RCP) after purification of Sep-Pak C18 cartridge was more than 99%. Both compounds showed pretty good stability in saline and fetal bovine serum, but cysteine challenge assay showed that the stability of 99mTc- HYNIC(EDDA)--Ala-BBN(7-14)NH2 was much better than 99mTc-HYNIC (Tricine)--Ala-BBN(7-14)NH2, with the RCP was more than 95% and less than 90%, respectively, at 24 h incubation at 37. Pattern of blood clearance of 99mTc-HYNIC(EDDA)--Ala-BBN(7-14)NH2 and 99mTc-HYNIC(Tricine)--Ala -BBN(7-14)NH2 was defined as two-compartment model, with T1/2冄 calculated to be 0.27 min and 1.55 min, and T1/2円 calculated to be 18.1 min and 29.7 min, respectively. Biodistribution revealed that the %ID/g of 99mTc-HYNIC(Tricine)- -Ala-BBN(7-14)NH2 was higher than that of 99mTc-HYNIC(EDDA)--Ala- BBN(7-14)NH2 for all of tissues at all time points of experiment; The uptake in kidneys for both compounds was relatively high, as the uptake in livers and intestines for 99mTc-HYNIC(Tricine)--Ala-BBN(7-14)NH2 was significantly higher than 99mTc-HYNIC(EDDA)--Ala-BBN(7-14)NH2, that meant that 99mTc-HYNIC(EDDA)--Ala-BBN(7-14)NH2 was mainly excreted through kidneys, while 99mTc-HYNIC(Tricine)--Ala-BBN(7-14)NH2 was excreted through both kidneys and hepatobiliary system. The above data demonstrated that 99mTc-HYNIC(EDDA)--Ala-BBN(7-14)NH2 possessed better chemical and biological properties.