The switching of resistance between two discrete values, known as random telegraph noise (RTN), was observed in individual single-walled carbon nanotubes (SWNTs) and C-60-filled SWNTs (the so-called peapods). The RTN has been studied as a function of bias-voltage and gate-voltage as well as temperature. By analyzing the features of the RTN, we identify three different types of RTN existing in the SWNT related systems. While the RTN can be generated by the various charge traps in the vicinity of the SWNTs, the RTN for metallic SWNTs is mainly due to reversible defect motions between two metastable states, activated by inelastic scattering with ballistic electrons. On the other hand, the noise for peapods can be attributed to the motion of C-60 molecules in hollow space of SWNTs. (c) 2005 Elsevier B.V. All rights reserved.