Dispersion and exfoliation of single wall carbon nanotubes (SWNTs) have been studied in poly(acrylonitrile) (PAN), poly(p-phenylene benzobisoxazole) (PBO) solutions, and composite fibers using transmission electron microscopy. As a result of polymer assisted dispersion and exfoliation, the average SWNT bundle diameter in SWNT/ PAN (5/95) was 11 nm, while the average diameter for the pristine SWNT bundles was about 30 nm. High resolution TEM of SWNT/PBO (10/90) composite fibers did not reveal the presence of SWNT aggregates or bundles, suggesting SWNT exfoliation as individuals. On the other hand, both oriented and unoriented nanotube bundles have been observed in SWNT/PBO samples containing 15 wt % nanotubes. Carbon nanotubes are 10(5) times more radiation resistant than flexible polymers such as polyethylene, and 10(5) times more resistant than highly radiation resistant polymers such as PBO. Therefore in the high resolution TEM study of nanotube/polymer composites, nanotubes can be observed long after the polymer has been damaged by electron radiation. (c) 2005 Wiley Periodicals, Inc.