Abstract: There is provided a polybenzazole fiber or film containing a basic organic compound in the form of a monomer or a condensate, selected from the group consisting of guanidines, triazoles, quinazolines, piperidines, anilines, pyridines, cyanuric acids, and p-phenylenediamine, m-phenylenediamine and a mixture thereof. This fiber has characteristics in that the X-ray meridian diffraction half-width factor is 0.3°/GPa or less, that the elasticity decrement (Er) attributed to change of molecular orientation is 30 GPa or less, and that the breaking strength is 1 GPa or more. This fiber can be used in staple fiber, a spun yarn, a woven or knit fabric, a felt material, a composite material, a cord, a rod, a fibrous sheet, a knife proof vest or a bullet proof vest.