Yarns of unidirectionally oriented discontinuous high-modulus fibers andwhiskers have been successfully produced in the laboratory by a modifiedvortex spinning process. Both core yarns in which the higher modulus fibersare overwrapped with organic or small diameter glass fibers and all- whisker-yarns have been spun. These yarns can be readily incorporated into plasticsas reinforcing agents by filament winding and related procedures. Thestrength of resulting composites is markedly superior to those of similarmaterials fabricated by other techniques due to well controlled fiberorientation and very uniform fiber overlap.