Integrin alpha(nu)beta(3) is an effective marker of angiogenesis in cancer, and alpha(nu)beta(3-)rspecific imaging can yield important details about this complex physiological process. We utilized the recently reported and highly alpha(nu)beta(3)-specific peptide, bicyclic RGD (bcRGD), as the basic structure of an in vivo alpha(nu)beta(3) imaging probe, and synthesized a radioiodinated form of bcRGD, namely [I-125]bcRGD, with high radiochemical purity (>99%) and high molar activity (81 GBq/mu mol). As expected, [I-125]bcRGD exhibited high selectivity for alpha(nu)beta(3) compared with alpha(nu)beta(5) and alpha(5)beta(1) in vitro. [I-125]bcRGD showed significantly higher accumulation in U-87MG cells (1.6% dose/mg) with high expression of alpha(nu)beta(3) compared to A549 cells (0.3% dose/mg) with only moderate expression. Furthermore, 30 min after administration to tumor-bearing mice, [I-125]bcRGD showed significantly higher accumulation in U-87MG tumors (3.8% ID/g) than in A549 tumors (2.1% ID/g), and the radioactivity accumulation ratios of U-87MG tumor/blood and U-87MG tumor/muscle were 4.0 and 6.0, respectively. These results highlight the promising properties of [I-123/(125)]bcRGD for use as an in vivo alpha(nu)beta(3) imaging probe, as well as the utility of bcRGD as a basic structure of molecular probes for both imaging and therapeutic applications. bcRGD may exhibit broad use in future theranostics applications targeting integrin alpha(nu)beta(3)-related diseases. (C) 2020 Elsevier Inc. All rights reserved.