Abstract Various fabric constructions for composite reinforcement were made from one particular fiber of the X-500 class of high-modulus organic fibers. This particular X-500 fiber (PABH-T) was a polyamide-hydrazide based on p-amino-benzhydrazide and terephthaloyl chloride. Three types of fiber yarns spanning a wide range of achievable tensile properties of the PABH-T X-500 fiber subclass were prepared: Type I, T/E/M1 = 12 (g/den)/2.5 (%)/650 (g/den); Type II, T/E/M1. = 8/6/350; Type m, T/E/M1. = 6/15/250. The effects of yarn denier, twist, sizing, and scouring on the tensile properties of the yarn were evaluated. Selected yarns were woven into fabrics using conventional textile looms. Fabric constructions were designed to provide fiber volumes equivalent to those of nylon and glass fabrics commonly used in reinforced composites. Physical properties of the woven fabrics compared favorably with those of the conventional reinforcing fabrics prepared from nylon 66 and glass. Fabric resin composite test specimen were prepared and their mechanical properties evaluated. A comparison was made with the mechanical properties of glass fabric/ resin composite laminates. The low specific gravity of X-500 fibers (1.45 g, cm2in this instance J in comparison to glass fiber (2.55) makes it possible to achieve high strength and high modulus composite structures of very light weight using X-500 type fabric reinforcing.