The electrical conductivity of the AGP513A, a ferromagnetic liquid, was studied in the frequency range of 0.1–12MHz and the temperature range of 20–50°C. For the frequency up to about 4MHz, the increase of electrical conductivity was weak. However, above this frequency, a rapid increase in electrical conductivity was observed. Three sub-ranges were distinguished in the loss tangent–frequency relationship. In the first sub-range, up to the frequency of 1MHz, the increase in the loss tangent was weak. In the second range, i.e. 1–4MHz, the increase in frequency and temperature did not affect the loss tangent, whereas in the third sub-range above 4MHz, it increased rapidly. Most probably, the dispersion in the range of 0.1–4MHz was the effect of aggregating of ferrofluid nanoparticles. Yet, for the frequencies above 4MHz, the aggregates of nanoparticles disappeared.