We report here the arc-production and spectroscopic characterization of fullerene-encapsulated metal atoms and metal-atom clusters. In particular, both solution and solid-stateelectron paramagnetic resonance (EPR) spectra of LaC82', YC82', SCC82' and Sc3 C82 have been obtained. Additional species containing rareearth atoms and clusters have been produced. The results suggest, for example, that the three scandium atoms in Sc3C82 form a molecule In the shape of an equilateral triangle — as was previously suggested for Sc3 molecules Isolated In a cryogenic rare-gas matrix. The spectraof the MC82 species (M =La, Y, Sc) exhibit small hyperfine couplings and g-values close to 2, suggesting that they can be described as a +3 metal cations within – 3 fullerene radical anion cages. Sc2C2n species — the most abundant metailofuilerenes In the scandlum-fullerene mass spectrum — are EPR-silent, even though Sc2 is EPR-actlve In a rare-gas matrix at 4.2K. A broader Implication of this work Is that production of macroscopic quantities of metal-containing fullerenes may make possible the fabrication of exotic new structures with regular arrays of metal atoms or clusters Isolated in fullerene molecules, resulting in new typesof host/guest nanostructured materials.