Unsaturated homopolyamide was prepared from 3-aminocinnamic acid (ACA) by the phosphorylation polycondensation method. In addition, various copolyamides were prepared from ACA and 4-aminobenzoic acid. Furthermore, an unsaturated homopolyamide was synthesized from 4-carboxycinnamic acid and 4,4’-diaminodiphenylmethane. The physical, chemical and thermal properties of the polyamides were correlated with those of the corresponding reference polyamides. The unsaturated polyamides showed an enhanced solubility in polar aprotic solvents and certain strong inorganic and organic acids compared to the reference ence polyamides. The X-ray diffractograms of polyamides showed some degree of crystallinity. Differential thermal analysis studies revealed melting of polyamides in the region of 237-292 degrees C. The crosslinked polymers obtained from unsaturated polyamides by curing at 260 degrees C for 20 h were remarkably more thermally stable than the reference polymers, being stable up to 310-366 degrees C in N-2 or air, and afforded a char yield at 800 degrees C of 66-80% in N-2 and 25-71% in air.