Abstract Several random copolymers composed largely of p-phenylene rings connected by hydrazide and, or carbonamide linkages yielded fibers exhibiting the high tensile strengths and the very high moduli characteristic of the fibers from wholly or partially ordered poiyamide-hydrazides having only p-phenyiene rings. The random copolymers showed the expected improved spinning performance relative to that of the all para-oriented poiyamide-hydrazides and certain polyamides containing only para-oriented phenylene rings.