Influence of fullerenes C-60 on the threshold voltage, dielectric, and conductivity properties of smectic A liquid crystal 4-nitrophenyl-4 '-decyloxybenzoic acid is investigated. It is shown that the transverse component of the real part of dielectric permittivity increases at the additive of fullerenes while the longitudinal component decreases. At this case, a maximum of dielectric absorption shifts to the high-frequency region. Conductivity increases at low frequencies and decreases at the high ones. Experimental results are explained on the base of the Maier-Meier theory for anisotropic liquids and also participation of fullerenes in ionic conductivity of liquid crystal.