Abstract The effect of leucine addition on the production yield of lysine by Corynebacterium glutamicum AJ-3462 was studied and a method of increasing a fermentation time while maintaining high lysine producing activity was developed. When leucine was not added during the lysine production phase, a high molar production yield of lysine from glucose of 35.6% was obtained. However, lysine production did not continue for a long time and almost stopped at around 90 h. When leucine was added to the medium in the fermentor at 24 h intervals, lysine producing activity was maintained for a long time; however, the production yield of lysine from glucose was reduced to 23.5%. When leucine was added at 30 h intervals, the production yield of lysine from glucose was improved to 32.9%. However, leucine addition did not recover lysine producing activity after 162 h. From these results, in order to extend the fermentation time while maintaining lysine productivity and production yield at high values, a leucine addition strategy was developed as follows. The initial leucine concentration was set as 0.1 g/ l. After depletion of leucine, it was added intermittently at 30 h intervals. The interval for intermittent addition was changed to 24 h when a decrease in cellular activity was recognized by on-line monitoring of the lysine production rate based on a metabolic reaction model. As a result, the fermentation time was extended to 174 h, and lysine productivity and total molar production yield of lysine from glucose became 0.104 g/ l/h and 29.2%, respectively.