Phytoremediation is a relatively inexpensive treatment strategy that can be used to stimulate the microbial populations that can degrade pesticides in soil in areas affected by sizeable pesticide spills, such as farmsteads and agricultural chemical dealership sites. In four greenhouse studies, researchers examined the degradation of two herbicides, atrazine and metolachlor, in soils with and without prairie grasses or herbicide-degrading bacteria co-applied with the grasses. Both grasses and inoculation with bacteria increased the degradation of atrazine in one soil, but not in another. Aging of residues (time before treatment) also decreased the effectiveness of grasses and bacteria. Vegetation increased the remediation of metolachlor, but the bacterial treatment was ineffective. This information will be useful to engineers and consultants engaged in remediation of some pesticide-contaminated sites and to state and EPA officials engaged in regulating cleanup of these sites.