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. Suitable substrates include medical devices, such as catheters, stents, brachytherapy devices and guidewires, or components thereof Medical devices capable of generating asymmetric, or targeted, radiation fields are also disclosed.