Paullinia belongs to the Sapindaceae and comprises 180 to 200 species, all neotropical lianas with the exception of P. pinnata occurring also in the African tropics. Two species, which have been reported to contain PuA, are used for the preparation of stimulating drinks: P. cupana H.B.K. and P. yoco Schultes & Killip. 'Guaraná' is the vernacular name for the plant species P. cupana and for the drugs prepared from the caffeine-rich seeds. 'Yoco' signifies both the stimulating extract made of the bark and the liana itself. Some years ago we screened 36 Paullinia species for their PuA content. Only one, namely P. pachycarpa, was found to contain little theobromine. It will not be discussed here.