[en] Objective: The aims of the study were to find out the optimal ¹³¹I labeling method with 17-allylamino, 17-demethoxygeldanamycin (17-AAG) and also to study its biodistribution in animals. Methods: ¹³¹I-17-AAG was prepared by the reaction of 17-AAG with Na¹³¹I in the presence of hydrogen peroxide. The labeling efficiency and the stability of ¹³¹I-17-AAG were measured by paper chromatograph. The biodistribution in the ICR normal mice was observed by the blood samplings and major organs that were taken out from mice at 0.5, 1, 4, 8, 24 h after ¹³¹I-17-AAG injection through tail veins. VX2 tumor was also implanted in rabbit liver for in vivo imaging with SPECT. Results: The optimal labeling conditions of 17-AAG with mi were determined. The labeling efficiency was 85.65%. The radiochemical purity of ¹³¹I- 17-AAG in acetoacetate solution was (96.51 ± 0.80)% after purification and its radiochemical purity in normal saline solution was (95.57 ± 0.09)%. The radiochemical purity could keep to 90% in normal saline after 5 d at 4 degree C. The biodistribution study in normal mice showed that the uptake (percentage activity of injection dose per gram of tissue, % ID/g) in liver and kidney was less than that in cholecyst [(3.0963 ± 1.3394) %ID/g] at 0.5 h post-injection, and the uptake in stomach and intestine reached to the highest level at 4 h post-injection. The SPECT images showed that the ¹³¹I-17-AAG was obviously concentrated in the tumor after injection at 2 h and 4 d, 6 d, 14 d with the highest tumor to non-tumor (T/NT) radioactivity ratio of 10.36. Conclusions: The labeling method of 17-AAG with ¹³¹I was successfully established. The ¹³¹I-17-AAG in normal saline had a good stability. The main biodistribution in mice was in digestive system and was excreted through the intestinal tract. The SPECT images showed that ¹³¹I-17-AAG might be a potential target-directed agent to the tumor. (authors)