The use of repellent products to prevent insect and arthropod bites is probably proportional to the public perception of the threat from biting arthropods, whether the threat is from annoyance or from the risk of disease. The connection between perception and use is logical when one considers that repellents are generally used as personal protection. It is the individual who usually decides whether or not to use a repellent, what kind of repellent to use, and how much to apply. The application to the individual makes entomological sense, in that the countermeasure is applied exactly where it is needed. On the other hand, the application by the individual presents a challenge to the professional who must educate and inform people with widely varied backgrounds on how to best protect themselves from biting arthropods. Insect and arthropod repellents are usually the first line of defense because they require no large equipment, no organized effort of community vector control, and they distribute the responsibility for protection to the individual. Today, there is great public concern throughout the world about vectorborne pathogens as human ecology seems to favor outbreaks of diseases as varied as West Nile fever, dengue, Lyme disease, malaria, leishmaniasis, and tick-borne encephalitis. In contrast to community vector control programs, insect and arthropod repellents give the individual control over exposure to biting arthropods. Professional researchers in public health are also interested in the development and useof repellents given the increasingly complicated requirements for pesticide use, the high cost of developing effective prophylactic vaccines and drugs, and the increase in incidences of arthropodborne diseases.