A correlation is proposed between the ratios:Y = πΔV≠/E(p)≠(where π is the internal pressure of a liquid, ΔV≠the volume of activationRT(∂ ln η/∂p)T, andE(p)≠the activation energy at constant pressure for viscous flow, or the corresponding quantities for diffusion) andX = E(ρ)≠/E(p)(whereE(ρ)is the "energy of thermal expansion", defined by:−R[∂ ln (ρ−1 − ρ0−1)/∂T−1]p). The first,Y, involves quantities measured at high pressures, whileXrequires only measurements at ordinary pressure. The correlation will permit estimation of viscosities and diffusion coefficients at high pressures from low-pressure measurements.