Positron emission tomography (PET) has been a research tool since the 1970s. Clinical applications today are primarily in the fields of oncology, neurology and cardiology. In the developed world a rapid expansion in PET facilities has taken place, owing to a dramatic increase in oncological indications since the 1990s. Today PET is widely available in developed countries and has also become available in a number of middle-income countries, including South Africa.