Agricultural productivity in Illinois relies on the practice of drainage. Subsurface drainage systems remove excess water from fields, but in the process agrichemicals such as nitrate-N are carried along a system of surface ditches and streams to potential drinking water supplies. Drainage research in Illinois is primarily concerned with reducing nitrate-N and pesticide loadings to ground and surface water outlets. Projects in Illinois have focused on the following topics: locating subsurface drainage systems; estimating nitrate-N loading from fields with random or irregular subsurface drainage systems; evaluating the effects of cropping management systems on the movement of nitrate-N; constructing wetlands to remove nitrate-N and other agrichemicals from subsurface drainage waters; and predicting surface flow and nitrate-N loading at the outlets of subsurface-drained watersheds.