After nearly 20 years in the clinic, the benefits of interferon-beta treatment in specific disease states are being recognized increasingly. Two major clinical studies completed within the past two years have firmly established the use of this drug in the treatment of multiple sclerosis. Its therapeutic activity in several indications, including acute and chronic viral hepatitis, has also been demonstrated; however, the general use of interferon-beta in these settings awaits the results of ongoing studies and the development of practical dosing regimens.