The 99mTc complex of NC100692 is being evaluated as a diagnostic agent for imaging of angiogenesis. We here report in vivo studies performed with NC100692 and 14C-labelled NC100692 using liquid chromatography coupled to either an ion-trap mass spectrometer or a radiochemical detector. Following injection of 14C-labelled NC100692, only the parent compound and no metabolites was observed in rat blood, whereas no parent compound and only 1 metabolite was observed in urine. Analysis of rat urine samples with liquid chromatography with mass spectrometric detection following administration of NC100692 verified the absence of the parent compound and showed the presence of 2 metabolites. The structures of the 2 metabolites were identified based on mass spectra and accurate mass determinations. The major metabolite was identified as the molecule obtained following hydrolytic cleavage at the end of the C-terminal amino acid of NC100692. The minor metabolite was identified as that obtained following removal of phenylalanine within the cyclic structure of the major metabolite.