Techniques have been developed for measuring the interfacial area in gas-liquid dispersions. It has thus been possible to measure the liquid-phase mass transfer coefficients in gas-liquid dispersions such as are produced in aerated mixing vessels, and sieve and sintered plate columns. The results have been combined with other published data for heat and mass transfer in liquid-liquid and solid-gas dispersions in which the dispersed phases are free to move under the action of gravity, and also with data on transfer by free convection from spheres. These data can all be correlated by (1) k(L)(N-Sc)(2/3) = hc/Cp rho c(Npr)(2/3) = 0.31 (Delta rho mu cg/rho c2)(1/3) For large gas bubbles which do not behave like rigid spheres as the smaller ones do (2) k(L)(N-Sc)(1/2) = 0.42 (Delta rho mu cg/rho c2)(1/3) If the particles of the dispersed phase are not free to move under gravity and transfer is due to turbulence in the surrounding fluid, (3) k(L)(N-Sc)(2/3) = hc/Cp rho c(Npr)(2/3) = 0.13 [(P/upsilon)mu c)/rho c2](1/4) where P/upsilon is the power dissipation per unit volume. This correlation applies to heat and mass transfer in mixing vessels where the solid phase is in the form of a single fixed submerged body and also predicts the small increase in mass transfer coefficients as the power dissipation level is increased beyond that needed for just completely suspending dispersed solid particles in mixing vessels. The correlation also applies to heat and mass transfer in turbulent fluids flowing through fixed beds of particles and through pipes.