Publisher Summary This chapter reviews the genetic control of pentose phosphate pathway enzymes in Drosophila. The main functions of the oxidative portion of the pentose phosphate pathway are to generate NADPH for fatty acid synthesis and pentose phosphate for nucleic acid synthesis. Because of this important role in carbohydrate and lipid metabolism, the pentose phosphate pathway has been the object of extensive metabolic and physiological studies in a variety of organisms, including Drosophila. The complete characterization of a biochemical pathway in an organism involves the accumulation of a variety of observations on the relative position of the pathway in the metabolism of the organism, on the factors that modulate its function, and on the molecular mechanisms by means of which this modulation is mediated. Although the characterization of the oxidative portion of the pentose phosphate pathway in Drosophila is far from complete, results obtained to date by combining traditional biochemical and genetic tools warrant an optimistic prognosis.