The structural parameters and strength properties of three types of new-generation precursor polyacrylonitrile fibers are comparatively analyzed. These fibers, after the carbonization process, can be used as implants supporting the process of bone reconstruction. They are characterized by a high tenacity ranging from 21 to 41 cN/tex. Tests and measurements have shown that the presence of nanoadditives causes a clear increase in the degree of fiber crystallinity. Moreover, the tenacity of the fibers can be considerably increased by the grinding of nanoadditive agglomerates with ultrasound. (c) 2007 Wiley Periodicals, Inc.