PHYTOREMEDIATION, or the use of plants to remediate contaminated soils and water environments, has recently become an area of intense study. Ten years ago there was a realization that the root zone of plants was special with respect to its capacity for biotransformation of organic molecules. The rhizosphere, as it was named, has since been studied for its important role in nutrient availability, as well as for the enhanced microbial degradation of pesticides, polynuclear aromatic hydrocarbons, and other synthetic chemicals. Plants impact contaminant reduction principally by providing an optimal environment for microbial proliferation in the root zone. This often leads to enhanced degradation of chemicals in soils that are vegetated, compared to nonvegetated soils. Contamination can also be reduced as a result of plant uptake into the tissue where it can be further degraded to innocuous substances, or removed from the site. In the latter case, plants can be used to extract contaminants from the environment, a process referred to as phytoextraction.