The occurrence of herbicides and other agricultural chemicals in groundwater continues to be a major concern in Iowa and across the country. Analytical capabilities have improved dramatically in the past twenty years, resulting in the ability to detect ever smaller quantities of chemicals (the vanishing zero). Detection of pesticides has been based primarily on conventional technology, such as gas or high-performance-liquid chromatographic methods. Although these methods are highly sensitive, they are also very expensive and time consuming. Immunoassay tests are alternative analytical methods that are also highly sensitive, but can be used by persons with little or no scientific background. The price of these tests also is within the range of most dealers and growers, approximately $150 for a kit that will analyze 10 to 15 samples. This paper will describe how immunoassays function and the potential areas where they might be used in agriculture.