Severe acute respiratory syndrome (SARS) has been reported in 30 countries and regions, with a cumulative total of 8,099 probable cases and 774 deaths as of July 31, 2003, according to the World Health Organization. In Hong Kong, People's Republic of China, 1,755 SARS cases and 299 deaths had occurred as of September 22, 2003. The authors analyzed data from the Department of Health, Hong Kong SAR. The data series includes details regarding sex, age, and chronic disease history. Using data from early March to September 22, 2003, the authors found that males had a significantly (p < 0.0001) higher case fatality rate than females did, 21.9% versus 13.2%; the relative risk was 1.66 (95% confidence interval (CI): 1.35, 2.05), and it was 1.62 (95% CI: 1.21, 2.16) after adjustment for age. Subgroup analysis was conducted by excluding health care workers (n = 386) from the analysis. The overall crude relative risk of mortality was 1.41 (95% CI: 1.15, 1.74), and the adjusted relative risk was 1.48 (95% CI: 1.10, 2.00). Thus, among SARS patients, males may be more severely affected by the disease than females are. This finding could be related to a nonuniform case definition of SARS disease, a different treatment regimen, a past smoking history, work-environment factors, or gender-specific immune-defense factors, for instance.