The heterocycle-containing aromatic
polyamide fibers of the invention are excellent in balance among mechanical characteristics, particularly balance among tensile strength, initial modulus and strength in the direction perpendicular to the
fiber axis, exhibit a high strength holding ratio under heat and
humidity, and are excellent in
flame retardancy, bulletproofness and
cutting resistance, as compared to conventional aromatic
polyamide fibers, and therefore can be favorably used in fields with severe mechanical characteristics and have stability to
environmental variation. Accordingly, the heterocycle-containing aromatic
polyamide fibers of the invention can be favorably used, for example, in fields including protective equipment, such as a helmet, a bulletproof
vest and the like, a
chassis for an automobile, a ship and the like, an electric insulating material, such as a
printed circuit board and the like, and other various fields.