Phosphorus-containing polyimide resins were prepared by reacting benzophenone tetracarboxylic acid dianhydride with (3-aminophenyl) methyl phosphine oxide (DAP). Copolyimides were also prepared using DAP and 4,2′,4′-triaminobenzanilide (TAB) and tris(3-aminophenyl) phosphine oxide (TAP) and pyromellitic dianhydride (PMDA). The homopolymer showed good thermal properties and little degradation below 400°C. The lapshear strengths of these polyimides depended on the backbone structure. Copolymerization improved thermal and mechanical properties. The glass-fabric-reinforced laminate prepared from one of the copolymer resins had a tensile strength of 43,430 psi.