Measurements of the nine adiabatic elastic constants of single-crystal forsterite are reported for the temperature range 300--1700 K at ambient pressure. The measured room temperature Cijs and their first temperature derivatives at ambient conditions are generally consistent with previous measurements, which were taken over a narrower temperature range. Slight nonlinear behavior is observed in the temperature dependence of the C11s, C22s, and C33s moduli. The resulting Hill-averaged bulk and rigidity moduli Ks and G are lower at 1700 K than predicted by linear extrapolation of low-temperature data. At 1700 K the new data give Ks=103.8¿1.1 GPa and G=61.3¿0.5 GPa. Isotropic elastic wave velocities have been calculated using the Hill averaging scheme over the range of temperatures measured. At T=1700 K and ambient pressure we find vp=7.79¿0.04 km s-1 and vs=4.48¿0.03 km s-1. The parameter (∂ℓnvs/∂ℓnvp)P is near to 1.2 and independent of temperature. Calculations are presented for elastic properties and other parameters important for the equations of state and anharmonicity of forsterite. Recent high-temperature thermal expansion measurements on a forsterite specimen from the same boule are used in this analysis. Effects of uncertainties in high-temperature thermal expansion data on these parameters have been evaluated and are discussed. ¿ American Geophysical Union