Few travel health measures are as controversial as the use of coca leaves at high altitude; yet, there appears widespread ignorance among health professionals and the general public about coca, its origins as well as its interesting and often flamboyant history. Equally, the cultural and traditional significance to Andean people is not recognised. The coca leaves contain many alkaloids, one of which, cocaine, has gained notoriety as a narcotic, leading to the mistaken idea that coca equals cocaine. This article contrasts coca with cocaine in an attempt to explain the differences but also the reasons for this widespread misconception. By its very nature, there may never be scientific ‘proof’ that coca leaves do or do not work for travellers at altitude, but at least a solid knowledge of coca, and how it differs from cocaine, provides a platform for informed opinions and appropriate critical views on the current confusing and contradictory legal situation.