Abstract: A bone cement is prepared by synthesizing a polymeric composition comprising poly(methyl methacrylate) cross-linked by copolymerization with tris(.omega.-methacryloyl) polyisobutylene. A powder is formed from the composition, and the final cement is prepared by mixing the powder with additional methyl methacrylate in the presence of a catalyst to form a dough-like material that is polymerized in situ to yield a cement useful for orthopedic purposes. Preferred embodiments employ tris(.omega.-methacryloyl) compounds within a particular molecular weight range, and which are present in the powder in particular amounts relative to the poly(methyl methacrylate) component therein.