Biologic response modifiers (BRMs) are substances that stimulate the body's response to infection and disease. The body naturally produces small amounts of these substances. Scientists can produce some of them in the laboratory in large amounts for use in treating infections and other diseases. This issue reviews the use of BRMs to treat infectious diseases as well as the infectious complications of BRMs used to treat non-infectious diseases. Articles on vaccines, antibodies, interferon, and other substances are included.