Solubilities of high-boiling components in supercritical fluid are reviewed from the point of view of process design. The authors described the solid-gas equilibria for binary systems, entrainer effects, supercritical fluid + two solid components for ternary systems. Furthermore, a prediction method by using an equation of state and molecular simulation was shown to calculate the solubilities of high-boiling components and the entrainer effects. Finally, the distinction for pressure dependence of the solubilities of high-boiling compounds between solid-gas and liquid-gas equilibria was discussed.