Direct hydrogenation of C-60 and C-70 was achieved without the use of a catalyst by exposing solid-phase fullerenes to high-pressure hydrogen gas (500-850 bar) at temperatures ranging from 573 to 623 K. Efficient production of C60Hx (X = 2-18) and C70Hy (y = 4-30) was identified by laser desorption Fourier transform mass spectrometry. Temperatures above 950 K in the presence of H-2 resulted in complete degradation of the fullerene samples. Gas-phase studies of the C60Hx+ ions revealed that these species will undergo proton transfer to pyridine, indicating that at least some of the hydrogens are bound exohedral to the fullerene cage and that the C60Hx species have lower ionization potentials than C-60 itself.