The synthesis of cylindrical polyamides by condensation of salts prepared from hexakis(4-carboxyphenoxy)cyclotriphosphazene (2) and diamines was investigated. Among the diamines used, p-xylylenediamine (4) gave the salt (5) composed of I : 3 2-4. The condensation of 5 at 240degreesC for 60 h gave a polyamide (6a) but some carboxyl groups remained without reaction. By adding excess 4 to 5 in a sealed tube, however, polyamide (6b), which showed no significant peak assignable to the carboxyl group in FT-IR and C-13-CPMAS spectra, was obtained. X-ray diffraction studies showed that 6a was amorphous but 6b has a high level of crystalline character. From these results and the structural feature of 2, it appears that 6b takes a three-dimensional cylindrical structure. The thermogravimetric analysis of 6b exhibited that the onset temperature of decomposition was 300 degreesC under both nitrogen and air atmospheres.