Biodiesel is the most important biofuel from both economical and technical points of view. Rice bran oil (RBO) with high free fatty acid (FFA) content offers important potential as an alternative low−cost feedstock for biodiesel production. The main purpose of this book is to compare and optimize the amount of oil extracted from rice bran. Different parameters (solid particle size, solvent type, extraction time, solvent to solid ratio, and pH of extraction solution), were studied to determine the optimum conditions. These conditions were: particle size less than 600 μm, temperature equal to 60°C for two hours extraction at pH 12.65, and solvent to solid ratio 5:1, using n−hexane as solvent. However, the storage period under humidity 80% can effect on increasing the free fatty acid content which was reached to 79.2% after one month at the same optimum conditions. The acid catalysis esterification process using high FFA oil led to high conversion (99%) at short time (90 min). The mathematical model of esterification reaction was developed and the predicted results explained a fair matching with the experimental results.