High-pressure investigations on fluid mixtures have been reviewed. Emphasis is on recent experimental studies conducted at the University of Bochum. These include: (I) fluid-fluid and solid-fluid phase equilibria including the critical behavior of binary mixtures, (2) liquid-liquid phase separations at very high pressures up to about 3 GPa in a diamond anvil cell, (3) the high-pressure phase behavior of ternary systems exhibiting cosolvency and miscibility windows, (4) the solubilities of dyestuffs in supercritical solvents by static or flow methods, (e) the determination of binary diffusion coefficients of low-volatile substances in supercritical solvents such as CO2 by a dynamic method, and (6) solvatochromism under pressure as a measure of solute-solvent interactions.