Interferon is a biological response modifier that regulates immune functions, slows cell proliferation, and inhibits virus replication. Interferon has produced promising results in the treatment of certain viral diseases and various tumors. It is rapidly becoming a part of conventional treatment regimes. Its various types, lots, and batches as well as its appropriate dilutions and doses must be familiar to nurse clinicians to assure safe administration and patient management. This article discusses the historical evolution of interferon, its clinical uses, and patient management issues.