Castrejon-Diez, Jaime (Tulane University School of Medicine, New Orleans, La.), Thelma N. Fisher, and Earl Fisher, Jr. Glucose metabolism of two strains of Mycoplasma laidlawii . J. Bacteriol. 86: 627–636. 1963.—Two strains of Mycoplasma laidlawii were incubated in systems containing d -glucose- C 14 ; carbon dioxide, acetate, pyruvate, and lactate were isolated from appropriate fluids after resting-cell and growth experiments. In resting-cell experiments, radioactivity recoveries were shown to be 95% for M. laidlawii A and 89% for M. laidlawii (Adler). By growth studies, the radioactivity recovery for M. laidlawii A was 83% and for M. laidlawii (Adler) was 90.5%. Low specific activities of the products as compared with the specific activity of glucose suggested cellular pools, or that the dissimilation of other substances present in the complex growth medium yielded products which contributed to the dilution factors. Enzyme studies added support to the hypothesis that glycolysis is operative in these organisms. Experiments with d -glucose- 1 - C 14 or d -glucose- 6 - C 14 as substrate suggested that the hexose monophosphate shunt may be functional in M. laidlawii (Adler), particularly since glucose-6-phosphate dehydrogenase, ribose-5-phosphate isomerase, and transketolase were demonstrated. This pathway is absent in M. laidlawii A.