Single doses of the traditional herbal treatment Panax ginseng have recently been shown to elicit cognitive improvements in healthy young volunteers. The mechanisms by which P. ginseng improves cognitive performance are not known. However, they may be related to the glycaemic properties of some Panax species. Using a double-blind, placebo-controlled, balanced crossover design, 30 healthy young adults completed a 10-min test battery at baseline and then six times in immediate succession commencing 60min after the day’s treatment (placebo, 200mg G115 or 400mg G115). The 10-min battery comprised a Serial Threes subtraction task (2min), a Serial Sevens task (2min), a Rapid Visual Information Processing task (5min) and then a ‘mental fatigue’ VAS. Blood glucose was measured prior to each day’s treatment, and before, during and after the post-dose completions of the battery. Both the 200 and 400mg treatments led to significant reductions in blood glucose levels at all three post-treatment measurements. The most notable behavioural effects were associated with 200mg of P. ginseng and included significantly improved Serial Sevens subtraction task performance and significantly reduced subjective mental fatigue throughout all of the post-dose completions of the 10-min battery.