This report summarizes data on water levels in 124 observation wells and provides information on well locations, depths, altitudes, and aquifers that they tap. Tabulated data include extremes of water levels for 1981 and for the period of record; pumpage of most major groundwater users in the State; and quality data on selected wells. The city of Lansing was the largest reported user of ground-water, pumping 8.6 billion gallons from the Saginaw Formation and glacial deposits.