The electrical conductivities (κ) of the ionic liquids 1-methyl-3-octylimidazolium hexafluorophosphate [OMIM]PF 6 , and 1-methyl-3-octylimidazolium tetrafluoroborate [OMIM]BF 4 , have been measured between 0 and 80°C and at pressures to a maximum of 196MPa. The temperature and pressure dependence of the conductivities are well represented by modified Litovitz and Vogel-Fulcher-Tammann (VFT) equations as is the case for the viscosity. The molar conductivity (Λ) is found to follow the fractional form of the Stokes–Einstein relationship with the viscosity (ΛT)∝(T/η) t , with t=0.96 for [OMIM]PF 6 and t=0.94 for [OMIM]BF 4 , independent of both temperature and pressure.