Nickel-zinc ferrites of different compositions Ni1-xZnxFe2O4 (x = 0.2, 0.3, 0.4 and 0.5) are prepared using flash combustion technique. The effect of frequency and composition on the ac-resistivity is studied for Ni-Zn ferrite samples sintered in the temperature range 1150°—1350°C. The physical properties, such as bulk density and porosity, are also studied for sintered ferrite samples. The experimental results indicate that the ac-resistivity (pac) decreases with increasing frequency. The ac-resistivity of the order of 105 Ω cm is obtained at 10 kHz in room temperature. These high values of resistivity make these Ni-Zn ferrites suitable for high frequency applications.