Having previously demonstrated that the polyimide derived from 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) and 1,2-bis(4-aminophenoxy)benzene [termed triphenyl ether catechol diamine (TPEC)l exhibited superior tensile properties in addition to good thermal properties, we now provide a preliminary assessment of the properties of the copolyimides prepared from BPDA, TPEC, and another aromatic diamine. The homopolyimides derived from BPDA and many aromatic diamines generally possessed good mechanical properties and thermal properties; however, they were insoluble in available organic solvents. In several cases, organosoluble DPDA copolyimides could be prepared from BPDA and equimolar mixtures of TPEC and another aromatic diamine. All the copolyimides could be formed into tough films with high moduli and strengths and, in most cases, high extensions to break.