Because of their unintended side effects, commercial synthetic pesticides are being replaced by biopesticides. The nature of biopesticides and their uses are detailed in this chapter. Already the use of biopesticides and other alternatives are having a major impact on the pesticide market in the United States and worldwide. Airborne residues can occur for biopesticides but tend to be less than for commercial pesticides of long-standing use. Thus, exposure to toxic pesticides will likely decrease in the future as these alternatives gain use.