This study reports on 10 cases of severe acute respiratory syndrome (SARS) in Hong Kong, China, diagnosed between February 22 and March 22, 2003. All patients were epidemiologically linked, with ages ranging from 35 to 72 years. The incubation period ranged from 2 to 11 days, and all patients presented with fever (temperature >38°C for over 24 hours), with most also experiencing rigor, dry cough, dyspnea, malaise, headache, and hypoxemia. Physical examination revealed crackles and dullness on percussion. Lymphopenia was observed in nine patients, and most had mildly elevated aminotransferase levels. Chest radiographs showed progressive air-space disease, with two patients dying of progressive respiratory failure. Histologic analysis of their lungs showed diffuse alveolar damage. No evidence of infection by Mycoplasma pneumoniae, Chlamydia pneumoniae, or Legionella pneumophila was found. All patients received corticosteroid and ribavirin therapy, with no clinical or radiologic efficacy. The microbiologic origin of SARS remains unclear. The study highlights the infectious nature of SARS, with fever and rapidly progressive respiratory compromise as key symptoms. The disease is highly contagious and can affect otherwise healthy individuals, even after minimal contact. The primary radiologic appearance of SARS is air-space shadowing, with subpleural focal consolidation and ground-glass opacities predominantly affecting the lower lobes. The clinical and radiographic features of SARS suggest a viral cause, as the incubation period is short, arguing against infection with M. pneumoniae or C. pneumoniae. The study emphasizes the importance of isolation precautions for patients suspected of having SARS and highlights the need for further research to identify the causative agent.This study reports on 10 cases of severe acute respiratory syndrome (SARS) in Hong Kong, China, diagnosed between February 22 and March 22, 2003. All patients were epidemiologically linked, with ages ranging from 35 to 72 years. The incubation period ranged from 2 to 11 days, and all patients presented with fever (temperature >38°C for over 24 hours), with most also experiencing rigor, dry cough, dyspnea, malaise, headache, and hypoxemia. Physical examination revealed crackles and dullness on percussion. Lymphopenia was observed in nine patients, and most had mildly elevated aminotransferase levels. Chest radiographs showed progressive air-space disease, with two patients dying of progressive respiratory failure. Histologic analysis of their lungs showed diffuse alveolar damage. No evidence of infection by Mycoplasma pneumoniae, Chlamydia pneumoniae, or Legionella pneumophila was found. All patients received corticosteroid and ribavirin therapy, with no clinical or radiologic efficacy. The microbiologic origin of SARS remains unclear. The study highlights the infectious nature of SARS, with fever and rapidly progressive respiratory compromise as key symptoms. The disease is highly contagious and can affect otherwise healthy individuals, even after minimal contact. The primary radiologic appearance of SARS is air-space shadowing, with subpleural focal consolidation and ground-glass opacities predominantly affecting the lower lobes. The clinical and radiographic features of SARS suggest a viral cause, as the incubation period is short, arguing against infection with M. pneumoniae or C. pneumoniae. The study emphasizes the importance of isolation precautions for patients suspected of having SARS and highlights the need for further research to identify the causative agent.