This work reports high-pressure viscosity measurements on two viscous liquids that may prove useful as high-temperature, high-viscosity reference materials, Krytox GPL102 and di(pentaerythritol) hexa(isononanoate). The perfluoropolyether oil, Krytox GPL102, is the subject of a round-robin comparison of high-pressure viscosity measurements on a specific sample being made by a group of laboratories worldwide employing a variety of viscometric techniques. Viscosity data are reported between (0 and 95) degrees C, at pressures to 226 MPa and viscosities between (6 and 4182) mPa.s. For the more viscous di(pentaerythritol) hexa(isononanoate), data are reported between (0 and 90) degrees C, at pressures to 203 MPa and viscosities between (34 and 2269) mPa.s. Correlations are provided using modified Vogel-Fulcher-Tammann (VFT) equations for both substances, a modified Litovitz equation for Krytox GPL102 and a modified Barlow-Lamb equation for di(pentaerythritol) hexa(isononanoate). Glass temperatures are estimated to be (178.2 and 218.1) K, respectively, based on the Angell equation relating the VFT parameters to T-g. Thermodynamic scaling is applied to both the experimental and reduced viscosities. The scaling parameters found are consistent with previous work on chain molecular compounds and esters.