The multistep process of angiogenesis offers several targets for therapeutic interventions. One molecular target structure is the alfa five beta three (av b3 ) integrin which is expressed on vascular endothelial cells and over-expressed in cancer tumor angiogenesis. To image neoangiogenesis in athymic mice with induced pancreatic, breast and prostate malignant tumors a new radiopharmaceutical was developed. The 99mTc-EDDA/HYNIC-cyclic-Arg-Gly- Asp-D-Phe-Lys (99mTc-cRGD) targets integrin receptors av b3 and was prepared with an average radiochemical purity > 95 %. 99mTc-cRGD shows high in vivo stability, fast blood clearance and rapid renal excretion in mice. There are statistical differences between tumor/muscle ratios for the 3 tumors studied. The highest tumor/non-target ratio was found in breast cancer (7.2 after 24 h) and a representative dorsal SPECT image was obtained where the tumor showed up very clearly over the background tissue. The high resolution of the image implies that 99mTc-cRGD will be of great value in nuclear medicine as a potential radiopharmaceutical for av b3 integrins receptor uptake and for imaging neoangiogenesis in neoplastic tissue and to follow up cancer tumor progression.