In early February 2003, the World Health Organization (WHO) began receiving reports of patients with a syndrome characterized by an atypical pneumonia with rapid progression to respiratory failure without an identified cause despite extensive diagnostic workups. Most of these reports pointed out that the outbreak started in Southern China, specifically in the Guandong Province. The initial outbreak in South East Asia has already spread to other Regions in Asia, Europe, North and South America, and South Africa. Many of these cases can be linked through chains of transmission to an index case from the Guandong Province who visited Hong Kong. Although the exact mode of transmission has not been clearly established, the etiology of this syndrome has already been identified. A novel Coronavirus has been identified by electron microscopy and molecular assays in multiple laboratories from respiratory specimens throughout the world. The syndrome has been defined as SARS (Severe Acute Respiratory Syndrome) by WHO, and is characterized by an incubation period between 1 and 10 days (average 5 days) and by a febrile phase that usually lasts approximately 3 days. During the respiratory phase that begins around day 3, patients start developing a dry cough, shortness of breath and hypoxemia. Mechanical ventilatory support is required in about 10 to 40% of cases and the case-fatality rate ranges between 3 and 16%. The laboratory findings in SARS cases include leukopenia, thrombocytopenia, and a rise in transaminases and lactic dehydrogenase levels. Treatment of SARS includes supportive measures and the empiric use of ribavirin. Respiratory isolation, use of respiratory masks, and compulsory hand hygiene constitute the principal preventive measures. The confirmation of a case can be performed at reference laboratories by serologic and molecular assays. From the onset of this epidemic Mexico established a surveillance system as well as clinical guidelines and recommendations for the identification, prevention of secondary spread, and medical management of suspicious and probable cases by health care personnel.