The crystal structure of α- and β-LiIO3 at room temperature was examined using X-rays diffraction. Differential thermal analysis (DTA) with different heating rates (5–50 K/min) in the range 300–600 K was performed. The activation energy of phase transition was calculated by two methods based upon DTA. The d.c. electrical conductivity (σ) and dielectric permittivity () of α-LiIO3 crystals were measured along both the a- and c-axes in the temperature range 300–580 K. Anomaly in the σ–T relationship was observed at the α→γ phase transition. The dielectric permittivity increased abruptly at T0=520 K indicating strong structural changes at this temperature. The J–E characteristics along a- and c-axes were measured below and above T0 and hence the type of conduction was estimated. The optical transmittance (Tr) and reflectance (R) at room temperature were also measured in the wavelength range 190–900 nm and hence the absorption coefficient (α), refractive index (n), optical band gap (Egopt) and the type of transition were estimated. The anisotropic character of the measured properties of LiIO3 are discussed