Countries worldwide face the threat of emerging infectious diseases. To understand the public's reaction to the use of widespread quarantine should such an outbreak occur, the Harvard School of Public Health, with the U.S. Centers for Disease Control and Prevention, undertook a survey of residents of Hong Kong, Taiwan, Singapore, and the United States. A sizable proportion of the public in each country opposed compulsory quarantine. Respondents were concerned about overcrowding, infection, and inability to communicate with family members while in quarantine. Officials will need specific plans to deal with the public's concerns about compulsory quarantine policies.