Severe acute respiratory syndrome (SARS) originated in Southern China in November 2002, and was brought to Hong Kong in February 2003. From Hong Kong, the disease spread rapidly worldwide but mostly to Asian countries. At the end of the epidemic in June, the global cumulative total was 8422 cases with 916 deaths (case fatality rate of 11%). People of all ages were affected, but predominantly females. Health care workers were at high risk and accounted for one-fifth of all cases. Risk factors for death included old age and comorbid illnesses, especially diabetes. The disease is caused by a novel coronavirus and is transmitted by droplets or direct inoculation from contact with infected surfaces. Contaminated sewage was found to be responsible for the outbreak in a housing estate in Hong Kong affecting over 300 residents. The mean incubation period was 6.4 days (range 2-10). The duration between onset of symptoms and hospitalisation was from 3 to 5 days. The relatively prolonged incubation period allowed asymptomatic air travellers to spread the disease globally. The number of individuals infected by each case has been estimated to be 2.7. Effective control of nosocomial transmission included early detection of disease, strict isolation of patients, practice of droplet and contact precautions and compliance with the use of personal protective equipment. Effective control of disease spread in the community included tracing and quarantine of contacts. Development of a validated diagnostic test and an effective vaccine as well as elimination of possible animal reservoirs are measures needed to prevent another epidemic.