The dielectric spectra ofn-decane-1,2-diol andn-undecane-1,2-diol have been measured with the use of time domain spectroscopy, in the temperature range covering the isotropic and liquid crystalline phases. In the isotropic and smectic phases a relaxation process was observed which could be described by the Cole-Cole equation with the distribution parameter α ≈ 0·20. It was established that the transitions from the isotropic to smectic phases were not accompanied by a step-wise change of the relaxation times. However, the activation energy increases markedly at the transition to the S*Bphase, whereas it does not change at the isotropic-S*Atransition. A discussion of the dielectric parameters obtained for these and other low molar mass diols is presented. It was found that the static dielectric permittivity and the activation barrier change systematically with the increase of the molecular length ofn-alkyl-1,2-diols.