Water levels, locations, depths, and aquifers tapped are given for 112 observation wells. Tabulated data include extremes of water levels for calendar year 1986 and for the period of record, pumpage of most major groundwater users in the State, and water-quality data from selected wells. The largest reported user of ground-water, the city of Lansing, pumped 7.6 billion gallons from the Saginaw Formation and glacial deposits in 1986.