Abstract: Radioactive coating solutions and sol-gels, and corresponding methods for making a substrate radioactive by the application of the radioactive coating solutions and sol-gels thereto. The radioactive coating solution comprises at least one carrier metal and a radioisotope, which may be soluble or insoluble, and may further comprise a reducing agent. The radioactive sol-gel comprises at least one metal alkoxide and a radioisotope, which may be soluble or insoluble. Methods of making a substrate radioactive by coating with radioactive coating solutions or sol-gels are also disclosed, including electrodeposition, electroless deposition, spin coating and dip coating. In a particular embodiment, the radioactive coating formed by the method is a composite coating. Radioactive substrates are also disclosed, comprising a substrate and one or more radioactive coatings, which coatings may be the same or different.