In this paper, the electrical transport mechanism and giant magnetoresistance (GMR) in advanced polyaniline (PANI) nanostructures and the related PANI nanocomposite systems are critically reviewed. The GMR phenomena in these materials have been theoretically interpreted by numerical models including forward interference model and wave-function shrinkage model. This knowledge could serve as a guideline for optimal design and manufacturing of conductive polyaniline-based GMR devices. (C) 2014 Elsevier Ltd. All rights reserved.