Clear, transparent (0.5–5.0 &mgr;), solution‐grown, single crystals of negative uniaxial LiIO3show no optically induced damage and remain stable in the temperature range 20°–256°C. The crystals are of point group 6 and are optically active and pyroelectric. We have measured the linear electrooptic coefficients in the visible and the optical activity in the infrared. For &lgr;1=1.0845 &mgr; phase‐matched second harmonic generation (PMSHG) occurred at &thgr;m=28.9° and this angle changed by less than 0.3° in the range 20–256°C. PMSHG was employed to determine the single domain quality of the crystals and to measure |d31(LiIO3)/d36(KDP) |=11. At 1.06 &mgr; we have measured the coherence lengths and the ratio of the nonlinear coefficients |d33/d31|=0.8.