Understanding the behavioral effects of herbal extracts presents a number of challenges to behavioral pharmacology. This review briefly summarizes these issues using guaraná (Paullinia cupana) as an example to illustrate certain key elements of this field. Guaraná has a long history of use as a stimulant in South America. Its purported stimulant effects have often been attributed to the presence of caffeine. However, guaraná's behavioral profile can be differentiated from that of caffeine. Recent evidence in humans and rodents suggests that other components of the plant (for example flavonoids) may contribute to its modulation of cognitive performance. This research is still in its infancy and further work is necessary in order to delineate whether guaraná has robust and replicable behavioral effects in humans. The contribution of different fractions of guaraná to its neurocognitive effects is unknown. Furthermore, whether acute advantages can be translated to chronic effects in cognitively vulnerable populations remains to be elucidated.