This paper reports an optimization of the Yamazaki–Higashi method of direct polyamidation from aromatic diacids and aromatic diamines. As a model reaction, the polycondensation between 4,4′-oxydianiline and isophthalic acid was studied in the presence of a phosphorylation agent and under microwave irradiation. This experimental study revealed that optimal results can be attained by using a great excess of pyridine as catalyst (pyridine-to-monomer ratio of 7), at moderate radiation intensity (200 W), and up to 25% (w/v) monomer concentration. Although the inherent viscosity achieved by microwave and by conventional heating was comparable, an exceptional reaction rate under microwave irradiation yielded a polyamide inherent viscosity of around 1 dL g^–1 in only a few minutes.