beta-Fructofuranosidase activity was found to be cell-bound in Streptococcus mitis ATCC 903. The following evidence suggests that induction functions as a regulatory mechanism for beta-fructofuranosidase in S. mitis: (1) on transfer of glucose-grown exponential phase bacteria to sucrose medium, the specific activity of beta-fructofuranosidase increased fourfold in the course of one generation; (2) other sugars had no stimulatory effect on the rate of synthesis of beta-fructofuranosidase; (3) the effect of sucrose on the rate of synthesis of beta-fructofuranosidase could be measured within a few minutes. Glucose, fructose and mannose repressed beta-fructofuranosidase. The addition of glucose to bacteria growing on sucrose repressed beta-fructofuranosidase for about one generation. The intracellular concentration of glucose was considerably increased during repression, while the intracellular concentration of glycolytic intermediates did not vary significantly.