As part of a continuing effort to prepare novel thermally stable high-performance polymers, poly(arylene ether pyrimidine)s have been prepared with 4,6-bis(4-(trimethylsiloxy)phenyl)pyrimidine and a series of activated bis(aryl fluoride)s using a catalytic amount of cesium fluoride in diphenyl sulfone. These polymers exhibited good thermal stability in both air and helium atmospheres with 10% weight losses in the range 480-540 degrees C. Moderate to high inherent viscosities (eta(inh) : 0.40-0.92 dL/g) were recorded, and clear pale yellow flexible fingernail creasable films were solution cast from these samples. A polymer in this series containing a phenylphosphine oxide linkage exhibited good thin film tensile properties and resistance to oxygen plasma. Model reactions with 4,6-bis(4-fluorophenyl)pyrimidine and p-cresol along with studies of this compound’s F-19 NMR shift values indicated sufficient capacity of the pyrimidine ring to activate aryl fluorides toward polymerization with bis(phenol)s. The pyrimidine bis(aryl fluoride) monomer was used to prepare a series of polymers with selected bis(phenol)s by potassium carbonate-mediated aromatic nucleophilic substitution reactions. One example containing the fluorene moiety exhibited a high inherent viscosity (eta(inh) : 0.80 dL/g); however, only brittle films could be cast from polymers prepared by this approach.