Widespread concerns have been raised about the possibility that exposure to the radiofrequency (RF) fields from mobile telephones or their base stations could affect people's health. Such has been the rapid growth of mobile telecommunications that there will be about one billion mobile phone users before 2005. Already there are more mobile than fixed-line users. Developing countries are establishing mobile telecommunications rather than the more expensive fixed-line systems. Thus, if there is any impact on health from mobile telephones, it will affect everyone in the world. The World Health Organization (WHO) established the International EMF Project in 1996 to evaluate the science, recommend research to fill any gaps in knowledge and to conduct formal health risk assessments of RF exposure once recommended research had been completed. In addition, the UK government established an independent expert group to review all the issues concerning health effects of mobile telephones and siting of base stations. Cancer has been suggested as an outcome of exposure to mobile telephones by some scientific reports. This paper reviews the status of the science and WHO's programme to address the key issues. In addition, the main conclusions and recommendations of the UK expert group will be summarised.