The intense use of soluble and mobile pesticides poses potential problems for nonpoint source contamination of streams and groundwater throughout the Midwestern United States. Previous studies have shown that runoff from fields immediately after application results in large concentrations of pesticides in surface water. This finding has been documented in several small basin studies but until recently has not been investigated at a multi-state scale to determine if pesticides cause contamination of surface water and groundwater on a regional scale. To address this concern, the US Geological Survey has conducted a series of regional-scale studies during the last 5 years to determine the occurrence, distribution, and transport of pesticides, particularly herbicides, in streams, reservoirs, groundwater, and rainwater in the midwestern United States. The purpose of this paper is to present a brief summary of the occurrence of herbicides and some of their metabolites in the water resources of the Midwestern United States based on results from these regional-scale studies.