Trends in atrazine detections and concentrations in Iowa surface and groundwater were reviewed relative to adoption of Best Management Practices and atrazine label changes designed to protect water resources. Analysis of a large statewide water monitoring database from 1982 to 1995 revealed statistically significant declines in both atrazine detection rates and concentrations in both groundwater and surface water. USGS monitoring of streams from 1989 to 1995 showed a decline in atrazine median concentration of almost 50%. Rural wells in Floyd and Mitchell Counties were sampled in 1986 and 198 7 and resampled in 1994, four years after the area was designated as an atrazine management area. Mean atrazine concentrations declined by 87%, and no wells exceeded the atrazine Maximum Contaminant Level (MCL) drinking water standard (6% of wells exceeded the MCL in 1986). Other studies also documented declines in atrazine detections and concentrations, which have been attributed to improved management of the herbicide. Exposure of Iowans to atrazine through drinking water is low. For the period 1994-2002, eleven Community Water Systems (CWS) utilizing the most vulnerable surface water sources were intensively monitored for atrazine. Only one CWS in one year exceeded the 3 ppb annual average drinking water standard. In an analysis of all Safe Drinking Water compliance monitoring in Iowa for the period 1993 through 2000, no CWS utilizing groundwater had an atrazine detection of 3 ppb or greater. No atrazine was detected in 90.2% of groundwater.