It is more convenient to handle a bundle of nanofibers or nanofiber yarn instead of a single nanofiber. Nanofiber yarns are robust enough to be handled without the requirement of very precise, sophisticated equipment. They can be deposited or transferred onto a substrate as orderly structures. Yarns (twisted and aligned) of several semiconducting ceramic nanofibers (ZnO, NiO, CuO, SnO2) were synthesized using electrospinning method. These yarns had average diameter ~10-30 um and their constituent fibers had the average diameter ~60-100 nm. Fabrication, characterization, and electrical properties of these semiconducting nanofiber yarns will be presented.