Polyhydrazides and poly(amide-hydrazide)s having inherent viscositie so f0 .31-1.17 dL g −1 were prepared from two ether-naphthalene-dicarboxylic acids, 4,4'-(1,5-naphthalene dioxy)dibenzoic acid (1,5-NDA) and 4,4'-(2,3-naphthalenedioxy)dibenzoic acid (2,3-NDA) with terephthalic dihydrazide, isophthalic dihydrazide, and p- aminobenzhydrazide via the phosphorylation polycondensation reaction. Except for one example, the hydrazide poly- mers were essentially amorphous and readily soluble in polar organic solvents such as N-methyl-2-pyrrolidone (NMP) and N,N-dimethylacetamide (DMAc). They could be cast into transparent, flexible, and tough films with good mechani- cal strengths from solution in DMAc. These hydrazide polymers exhibited glass-transition temperatures (Tgs) in the range 179-190 ◦ Ca nd could be thermally cyclodehydrated into the corresponding poly(1,3,4-oxadiazole)s and poly(amide- 1,3,4-oxadiazole)s in the solid state at elevated temperatures. The oxadiazole polymers had Tg so f228-242 ◦ C( by differential scanning calorimetry) and 10% weight loss temperatures above 500 ◦ C, as revealed by thermogravimetric