The dielectric constant (epsilon') and dielectric loss factor (epsilon") for the ferrite Co1-xZnxLayFe2-yO4; 0.1 less than or equal to x less than or equal to 1.0 were measured at different frequencies (100 kHz to 5 M:Hz) and different temperatures (300-850 K). More than one type of polarization participates in the dielectric process, Maxwell Wagner polarization is the one participating in the high temperature region. The electrical conductivity measurement showed that there is more than one conduction mechanism participating in conductivity. The hopping mechanism either by holes or electrons or both is the predominant one. The increase in conductivity is due to the thermally activated mobility and not to thermal creation of additional mobile charge carriers. The replacement of Fe3+ by La on octahedral sites and the presence of Co2+ as well as Zn2+ ions on the tetrahedral sites play a significant role in the electrical and magnetic properties behavior of the investigates samples. The values of the activation energy obtained indicate the semi-conducting behavior of the investigated ferrite. (C) 2003 Published by Elsevier B.V.