The utilization of glucose by proliferatingPenicillium digitatumcells has been examined by the radiorespirometric method. Glucose is catabolized by this organism mainly (77%) by way of the Embden–Meyerhof–Parnas pathway in conjunction with the tricarboxylic acid cycle and CO2fixation processes. A minor portion (23%) of the administered glucose is utilized via an oxidative route involving a C1–C5cleavage. Pathway estimations on the basis of CO2production and glucose consumption were also discussed.