This is an award to provide support for a workshop on nitrate contamination of groundwater, exposure, consequences and control. The workshop will be held at the University of Nebraska, Lincoln from September 10-14, 1990 and is being principally supported by the NATO Scientific Affairs Division. This award from NSF will permit extending support for participation in this conference by Dr. Jaroslav Vrba, Chairman of the Commission for Groundwater Protections of the International Association of Hydrogeologists (Czechoslovakia) who will speak on Hydrogeological System Nitrate Contamination - Origin and Control in Eastern European Countries, or by an alternative person on a similar topic. Results of this workshop are expected to provide guidance to the program in its support of research on groundwater pollution from substances that contribute nitrogenous substances to groundwater aquifers.