Two new water-soluble Gd-containing endohedral metallofullerenes [ScxGd3-xN@C80Om(OH), (x = 1, 2; m; approximate to 12; n approximate to 26)] were synthesized in a simple one-step reaction and characterized by Fourier transform (FT)-IR as well as X-ray photoelectron spectroscopy (XPS). Their observed longitudinal relaxivities (RI) for water protons are 20.7 and 17.6 mM(-1) s(-1), respectively, which are significantly higher than that of the commercial magnetic resonance imaging (MRI) contrast agent (Gd-DTPA, 3.2 mM(-1) s(-1)). These results indicate these trimetallic nitride endohedral fullerenols are potential next-generation high-efficiency MRI contrast agents.