In the past few months, ayahuasca has received quite a bit of coverage in the lay press. Ayahuasca is a South American hallucinogenic tea that is gaining popularity in Europe and North America. In the Netherlands, ayahuasca is usually used in a group ceremony called an 'ayahuasca ceremony'. Use of ayahuasca is not associated with the development of substance dependency. The side effects of ayahuasca are considered mild. We describe a 36-year-old woman who developed severe hyponatremia after participating in an ayahuasca ceremony. We also discuss the mechanism of action, the effects, the therapeutic potential and the risks of this hallucinogenic agent.