It is evident that almost any form of solid deposition in facilities and pipelines during the production and processing of oil and gas has undesirable economic and operational effects. These precipitating solids can be any one of pure solids, hydrates, waxes, asphaltenes, scales, or any mixture of them. The wax crystals are one of the most common and problematic solids. Wax precipitation can occur for gas condensate, light oil, and heavy oil fluids at temperatures as high as 338.7 K, and therefore it makes this study essential for oil and gas industries. In this book, the wax precipitation from various oil and gas is studied, using a modified multisolid- phase thermodynamic model. In addition, this book presents two and three phase equilibrium calculations to estimate the amount of the wax precipitated and the wax appearance temperature. Furthermore, the effects of pressure and temperature on the wax formation for both crude oil and gas systems were investigated. On the whole, it covers various aspects of the subject, hence can be tailored for engineers and researchers both in universities and in oil/gas industries.