The intracellular rate‐limiting capability of phosphofructokinase in baker's yeast (Saccharomyces cerevisiae) fermentation is investigated using the reaction path analysis discussed by Liao and Lightfoot in a previous article. It is found that the yeast cells under our experimental conditions indeed exhibit the characteristic behavior, and the characteristic reaction path on the G6P‐ATP phase plot is determined for cells fed with different sugars, cells of different strains, and cells in the transition period following rehydration. Results suggest that phosphofructokinase does not limit the CO₂ production rate of the cells under investigation. However, it is not present in a great excess either: ca. 80% of phosphofructokinase activity is utilized by the glycolytic pathway of the cell under investigation.