Broadband dielectric spectroscopy (10(-1) to 10(6) Hz) in combination with TSDC were employed to study the relaxations and the conductivity phenomena in polyamide 6/CaCO3 composites loaded with different contents and particle sizes of treated and untreated CaCO3. In addition to the primary alpha-relaxation associated with the glass transition, significant interfacial relaxation and ionic conduction processes have been revealed. The temperature dependence of the relaxation rates of alpha-relaxation and Maxwell-Wagner-Siller-process as well as that of the hopping rate of the conduction mechanism were found to follow the Vogel-Fulcher-Tammann-model. This may support the idea that the three mechanisms are not completely independent. The modification of the filler does not add any effect on the resistivity values. (C) 2011 Wiley Periodicals, Inc. J Appl PolymSci 122: 2039-2046, 2011