Immigrants and refugees are at risk of infectious diseases (IDs) that are rare in the United States. Screening and treatment before entry into the United States are required for some of these diseases, whereas quarantine is mandated for others. The Centers for Disease Control and Prevention has published specific recommendations for the evaluation and treatment of immigrants and refugees before and after they arrive in the United States. In addition, immigrants and refugees who return to their home countries are at greater risk of IDs than other travelers. Health care professionals are required to report certain IDs to state or local health departments.