AC impedance measurements have been carried out on (NH4)(2)SO4 single crystals for the temperatures from 300 to 473 K and frequency range between 100 Hz and 4 MHz. The results reveal two distinct relaxation processes in the sample crystal. One is the dipolar relaxation with a peak at frequency slightly higher than 4 x 106 Hz. The other is the charge carrier relaxation at lower frequencies. The frequency dependence of conductivity is described by the relation sigma(omega) = B omega(n), and n = 1.32 is obtained at temperatures below 413 K. This value drops to 0.2 and then decreases slightly with increasing temperature. The dipolar response of the (NH4)(2)SO4 single crystal under an ac field is attributed to the reorientation of dipoles. The contribution of charge carriers is increasing substantially with increasing temperature at temperatures above 413 K. The temperature variation of conductivity relaxation peaks follows the Arrhenius relation. The obtained activation energy for migration of the mobile ions for (NH4)(2)SO4 single crystal was 1.24 eV in the temperature range between 433 and 468 K in this intrinsic region. It is proposed that the NH4+ in the sample crystal has the contribution to the electrical conduction. (C) 2009 Elsevier B.V. All rights reserved.