Objective: To explore the labeling techniques of monoclonal antibody against pro-gastrin-releasing peptide(31-98) (D-D3) and its single chain antibody (scFv) with 131I.To study the feasibility of radioimmunology imaging in nude mice bearing SCLC using 131I-D-D3 and 131I-anti-ProGRP(31-98) scFv.Methods: Chloramine-T method was used for 131I labeling D-D3 and scFv.The labeling efficiency and radiochemical purity were measured by paper chromatography.Radiochemical purity was measured at different time points to determine the stabilities of labeling products.Healthy Kunming mice were sacrificed at different time points after being respectively injected with 131I-D-D3 and 131I-anti-ProGRP(31-98)scFv through tail veil.The blood and organs were harvested for calculating dose per gram of tissue (%ID/g).In the same way, organs and tumor tissue of nude mice bearing SCLC were harvested for calculating %ID/g and tumor/non-tumor (T/NT) ratio.After injection of 131I-D-D3, continuous images of the nude mice bearing SCLC, stomach cancer,breast cancer, pancreatic cancer and lung adenocarcinoma were respectively carried out at different time points.Transplantation tumor images were then observed and tumor/base (T/B)ratios were calculated.Results: The labeling rates of 131I-D-D3 and 131I-anti-ProGRP(31-98)scFv were 86% and 93.35%,and the radiochemical purity were 99.27% and 98.49%, respectively.After incubation at 37℃ for 24h, the radiochemical purity were 93.5% and 94.59%, respectively.Meanwhile, after incubation with rat serum for 24h, the radiochemical purity were 64% and 85.16%, respectively.Both of 131I-D-D3 and 131I-anti-ProGRP(31-9s)scFv were mainly eliminated through the liver and kidney metabolism in vivo in the normal Kunming mice and nude mice bearing SCLC.The peak uptake of 131I-D-D3 and 131I-anti-ProGRP(31-98) scFv in renograft tumor of SCLC were at 72h and 24h after injection, respectively.After injection of 131I-D-D3, radioactive concentration was observed in tumor tissues of nude mice bearing SCLC, gastric cancer, breast cancer and pancreatic cancer.However, no radioactive concentration was observed in tumor tissues of nude mice bearing lung adenocarcinoma.Conclusions: Both 131I-D-D3 and 131I-anti-ProGRP(31-98)scFv could effectively target SCLC,therefore was a promising radioimmunoimaging and radioimmunotherapy radiopharmaceutical for SCLC.