Bioventing is the process of aerating soils to stimulate in situ biological activity and promote bioremediation. Bioventing typically is applied in situ to the vadose zone and is applicable to any chemical that can be aerobically biodegraded, but to date has been implemented primarily at petroleum-contaminated sites. Through the efforts of the U.S. Air Force Bioventing initiative and the U.S. EPA Bioremediation Field initiative, bioventing has been implemented at more than 150 sites and has emerged as one of the most cost-effective and efficient technologies currently available for vadose zone remediation of petroleum-contaminated sites. This document is a culmination of the experience gained from these sites and provides specific guidelines on the principles and practices of bioventing.