Studies have been made on the pathways of glucose metabolism in the rat submaxillary gland utilizing many techniques in order to reach a closer approximation to what occurs in the cell in vivo. Cell-free extracts contained enzymes for the metabolism of glucose through the Embden-Meyerhof pathway and the pentose-phosphate cycle; however, the activity of glucose-6-phosphate dehydrogenase (d-glucose-6-phosphate: NADP oxidoreductase, EC 1.1.1.49) was very low, which may be the limiting factor for direct glucose oxidation via pentose phosphate pathway. Tracer studies were carried out with glucose labeled in various positions to estimate the yield of 14CO2, the corrected specific activity of lactate formed from [1-14C]-glucose and [6-14C]glucose and the randomization of the labeled carbon of [2-14C]-glucose and [1-14C]glucose in the other carbons of lactate. Results indicate that in rat submaxillary gland the main pathway for glucose metabolism is the Embden-Meyerhof glycolytic process; the pentose-phosphate cycle operates to the extent of less than 10%, and the Entner-Doudoroff pathway is absent in this tissue. © 1964.