This volume contains data on diffusion in pure liquids and solute in solvent systems. Diffusion processes are widespread phenomena in nature, of which mass diffusion is the most important one, in particular in liquids. The corresponding diffusion coefficients strongly depend on concentration, temperature, pressure and density. Contrary to the measurement of viscosity or heat transfer, where a few well developed experimental methods exist, we find a wide spectrum of different methods for measuring mass diffusion coefficients ranging from NMR spectroscopy, scattering, holography, interferometry, chromatography, diffusion through diaphragm and in capillary systems, and electroanalytical methods.After an introduction about the selection and normalization of data, in its first part this volume presents the most important measurement methods, followed by a second part on diffusion coefficient data depending on the various parameters.