Solubility is the most important criterion affecting the efficacy of most of the supercritical fluid processes.For example,the solubility can have a direct impact on the rate,yield,design,and economy of the process.Depending upon the process of interest,either a high solubility or extremely low solubility may be desired.For example,a high solubility is required in the supercritical extraction processes.On the other hand,a low solubility is required for CO2/organic solvent mixtures used in the supercritical antisolvent precipitation processes to manufacture particles [1].Here the solubility affects yield,cost,and,most importantly,the size and morphology of the product.In the precipitation processes,nucleation is a strong function of supersaturation,which,in turn,depends upon the solubility.Solubility can have a remarkable effect on the precipitation kinetics.Similarly in rapid expansion of supercritical solution to produce particle,solubility plays a key role.Solubility is typically defined as mole fraction (y2) or weight fraction (w2) of solute in the supercritical fluid,which is in equilibrium with the bulk solute.Various methods to measure solubility in supercritical fluids have been employed by many researchers worldwide [2,3].These methods can be divided into two major categories:(A) static,and (B) dynamic.Here,we are going to introduce all the methods and equipments to measure the solubility of solid and liquid in supercritical carbon dioxide.Solubility behavior as well as the sources of solubility data will also be discussed.