There is growing evidence that certain plants have evolved to contain bioactive compounds that can modulate behaviour, including cognitive performance. This chapter briefly summarises the evidence pertaining to selected herbal extracts ginseng, Ginkgo biloba, Salvia, L-theanine, green tea catechins, Bacopa and guarana. The focus is on evidence from well-controlled human trials examining the acute effects of supplementation in healthy adults. Although not discussed here, it should be noted that there is emerging evidence that some herbal extracts may also have chronic cognitive benefits in various clinical and non-clinical populations. Certain botanical extracts have reliable cognition-enhancing properties in various populations. These appear to be similar in magnitude to the effects of pharmaceutical cognitive enhancers. In some cases, the mechanisms of action are reasonably well established, for example, pro-cholinergic (e.g. cholinesterase inhibiting) effects of sage. In most cases, multiple synergistic actions are likely to be involved. One constant challenge for the psychopharmacology of herbal extracts is the use of standardised extracts to allow rigorous and replicable evaluation of their behavioural properties.