The increase in the consumption of energy derived from fossil sources, together with the high emissions of atmospheric pollutants, has caused environmental concerns about global energy security. These concerns have stimulated a worldwide search for new energy sources. Among these options, fatty acid alkyl esters known as biodiesel have emerged as an interesting alternative to petrochemical diesel, due to their characteristics such as: biodegradability, lower toxicity (lower sulphur and aromatic content) and sustainability, as most of the raw materials used in biodiesel synthesis are triglycerides found in oleaginous plants, animal oils and fats. Based on this, the aim of this book was to study the oxidative degradation of methyl esters obtained from pequi oil in natura and after different frying times, evaluating the conversion of triglycerides into esters, induction period, acidity index, specific mass at 20°C, visual aspect and peroxide index.