Kombucha has become a popular complementary remedy. The aim of this systematic review was to critically evaluate the evidence related to its efficacy and safety. Computerised literature searches were carried out to locate all human medical investigations of kombucha regardless of study design. Data were extracted and validated by the present author and are reported in narrative form. No clinical studies were found relating to the efficacy of this remedy. Several case reports and case series raise doubts about the safety of kombucha. They include suspected liver damage, metabolic acidosis and cutaneous anthrax infections. One fatality is on record. It was concluded that the largely undetermined benefits do not outweigh the documented risks of kombucha. It can therefore not be recommended for therapeutic use.