International adoptions have become increasingly common in the United States. Children awaiting international adoption and families traveling to adopt these children can be exposed to a variety of infectious diseases. Compared with the United States, foreign countries often have different immunization practices and methods of diagnosing, treating, and monitoring disease. Reporting of medical conditions can also differ from that of the United States. The prevalence of infectious diseases varies from country to country and may or may not be common among adopted children. The transmission of tuberculosis, hepatitis B, and measles from adopted children to family members has been documented. Furthermore, infectious organisms (e.g., intestinal parasites), bacterial pathogens (e.g., Bordetella pertussis and Treponema pallidum), and viruses (e.g., human immunodeficiency virus and hepatitis viruses) may cause clinically significant morbidity and mortality among infected children. Diseases such as severe acute respiratory syndrome or avian influenza have not been reported among international adoptees, but transmission is possible if infection is present. Family members may be infected by others during travel or by their adopted child after returning home. Families preparing to adopt a child from abroad should pay special attention to the infectious diseases they may encounter and to the precautions they should take on returning home.