in research are helping to reduce and eradicate disease. For example, ivermectin is successfully used to treat and prevent river blindness, which affects or threatens 100 million people in some of the poorest areas of the world. Other spectacular success stories include the discovery of antiulcer drugs such as cimetidine and ranitidine, which not only reduce ulcer-related pain and morbidity but also decrease the need for expensive hospitalization.

The challenges to biomedical science in the last decade of the twentieth century are imposing; they include autoimmune diseases, mental illness, cancer, geriatric disorders, diabetes, and viral infections. In each case, major input must be obtained from chemists and chemical engineers if we are to meet these challenges. No current challenge is greater than that of AIDS, against which a concerted, multipronged attack is under way. The chemical synthesis of the life-extending drug AZT was an important first step in this battle.

Most likely, someone in your family has used a man-made device for the treatment of some medical condition: perhaps an inner ear implant, an artificial hip, or maybe just contact lenses. The development of synthetic replacements for joints, ligaments, lenses, and teeth is certain to become more important as the percentage of older people in our society increases. Battery-driven cardiac pacemakers now provide rhythm for defective biological control systems, other heart-assist devices aid in the recovery of patients with hearts damaged by disease or infarction, and polymerbased replacement parts ranging from small blood vessels to artificial hearts are on the horizon.

Contact lens technology, including the new, safer materials used in soft and extended-wear lenses, is the result of extensive research and development efforts by chemists and chemical engineers.

Hybrids of biological and man-made systems are also being explored. One example is the use of implanted