The absorption coefficient of LiIO3has been measured at 300°, 80°, and 7°K for the ordinary and extra‐ordinary ray. The corresponding indices of refraction at 300°, 80°, and 17°K were also determined. Upon cooling from 300° to 7°K, the absorption coefficients decrease drastically in the 10–150‐cm−1spectral region. At 7°K the absorption coefficient is less than 1 cm−1for frequencies up to 80 and 90 cm−1forE∥candE ⊥ c,respectively. This characteristic is important for far‐infrared generation by mixing of two laser frequencies.