The behavior in interfacial polycondensation of 4,4’-methylenedianiline or 4,4’-oxydianiline (ODA) in water with dimethoxycarbonyl terephthaloyl chloride (DCMTC) in dichloromethane with benzyltriethylammonium chloride (BTEAC) as a catalyst was examined with a Fourier transform infrared spectrophotometer, attenuated total reflectance, an ultraviolet spectrophotometer, and a scanning electron microscope. When the ratio of the DCMTC concentration to the ODA concentration was about 2 : 1, the interfacial polymer obtained had relatively high inherent viscosity. With the addition of a suitable amount of sodium carbonate and BTEAC, the interfacial polymer obtained had relatively high inherent viscosity. The polymer film grew toward the organic phase from the interface region until the reaction was over. The surfaces of the films adjacent to the water phase were composed of the polymer having a higher molecular weight and were denser in morphology than those of the films adjacent to the organic phase.