Nitrate-nitrogen (nitrate-N) in groundwater is a potential problem in many parts of Kansas. From 1990 to 1998, 747 water samples were collected from domestic, irrigation, monitoring, and public water supply wells primarily from the western two-thirds of the state, and analyzed for nitrate-N by the Kansas Geological Survey. Nitrate-N concentrations of the 747 samples analyzed range from 29% with less than or equal to 3 mg/L, 51% between 3 and 10 mg/L, and 20% greater than or equal to 10 mg/L. Factors that show a statistically significant relationship with the occurrence of nitrate-N in Kansas groundwater in this assessment include geographic area of the state, depth of well, and age of well. Nitrate-N levels of wells screened in the High Plains aquifer in south-central Kansas showed a statistically higher concentration than samples collected from the High Plains aquifer in the western portion of the state. Comparison of nitrate-N with depth of well indicated that shallower wells throughout the state generally have higher nitrate-N values than deeper wells. Irrigation wells older than 1975 showed statistically higher nitrate-N concentration than wells installed during and since 1975, possibly related to changes in well-construction practices and regulations that occurred in 1975. ?? 2000 International Association for Mathematical Geology.