A process for making cerium-containing nanoparticles with biocompatible stabilizers is described, wherein an aqueous reaction mixture comprising cerous ion, citric acid, a stabilizer (chelator) selected from the group consisting of nitrilotriacetic acid, ethylene glycol tetraacetic acid and diethylenetriaminepentaacetic acid, and an oxidant, is provided, followed by a heating step to effectively form the nanoparticles. These biocompatible nanoparticles can be used to treat oxidative stress related diseases and events, such as ischemic stroke.