As part of a program to develop resins for high-performance/high-temperature aerospace structural applications, preliminary neat resin properties of naphthylethynyl terminated imide oligomers were determined and compared with the corresponding phenylethynyl terminated imide oligomers. Prior to oligomer work, four naphthylethynyl and phenylethynyl phthalimide and four naphthylethynyl and phenylethynyl naphthalimide model compounds were prepared and their thermal properties compared. The naphthylethynyl end-caps in N-phenyl-or N-naphthylphthalimide model compounds reacted at a lower temperature than the phenylethynyl end-cap in the same compounds, as previously reported. In contrast to these results, replacement of the phthalimide groups with naphthalimide groups showed that the phenylethynyl end-cap reacted at a lower temperature than the naphthylethynyl end-cap. Four aryl ethynyl terminated imide oligomers having the same imide backbone and molecular weight but different terminal units were prepared and the properties of the cured polymers compared. Phenylethynyl end-capped or naphthylethynyl end-capped oligomers, cured at 340 or 371 degreesC, exhibited similar tensile properties in thin films. The chemistry and properties of these materials are presented.