The synthesis of nylon 4,T from tetramethylenediamine and a terephthalic acid derivative was studied in a two step-process: prepolymerization, followed by postcondensation in the solid state (4 h, 290°C). The prepolymers were prepared by the nylon salt method, ester polymerization method, interfacial method, and a low temperature solution method. A maximum ηinh of 1.52 was obtained. From a solution in trifluoroacetic acid, films were cast and on these films we studied its IR spectrum, WAXS, and melting behavior with DSC. A boiled up sample had a double melting transition at 434 and 475°C and a ΔH0 of 130 J/g.