As part of an ongoing effort to develop processable, high-performance resins for aerospace applications, a phenylethynyl-terminated imide (PETI) oligomer designated LaRC(TM) PETI-1 was developed. This reactive oligomer has a number-average molecular weight of 6300 g/mol and a T-g of 218 degrees C. Upon curing the reactive oligomer at 350 degrees C for 1 h, a tough material with a T-g of 249 degrees C was obtained. The properties of cured PETI-1 in the form of composites, adhesive specimens, thin films, and neat resin moldings are excellent. The synthesis, characterization, and mechanical properties of this polyimide are discussed.