The temperature and frequency dependence of dielectric constant (epsilon') and dielectric loss (epsilon") is studied for different samples of polyaniline (PANI), doped with different concentration of sulfamic acid in the frequency range (10-100 kHz) and temperature range (300-400 K). The do conductivity has also been measured to see the effect of sulfamic acid and the conduction mechanism has been explained by the propagation of polaron through a conjugated polymer chain due to shifting of double bonds (alternation), which gives rise to electrical conduction. (c) 2006 Elsevier B.V. All rights reserved.