Laser desorption time-of-flight (LDTOF) and field desorption (FD) mass analyses were carried out on plasma-polymerized C-60 films prepared by subliming C-60 under an argon (Ar) plasma. In the LDTOF analyses, peaks attributable to C-60 polymers with more than 10 C-60 units were detected. The mit values of the peak maxima of the polymers suggest that during the polymerization process four carbon atoms were eliminated in a transformation between two C-60 molecules, in the most frequent case. The cross-linking between C-60 molecules was theoretically examined at the semiempirical MNDO/AM-1 level, and the most intense peak m/z = 1393 in dimer mass range was assigned to a C-116 molecule with D-2h symmetry.