Ground-water baseflow to six subreaches of the Upper Mississippi River were estimated for July 1988, a period of drought. Ground-water baseflow to each subreach was estimated on the basis of streamflow gains determined from records of daily discharge at gaging stations. Streamflow gains were adjusted for estimated inflow from tributaries, municipal and industrial discharges, withdrawals, and evaporation. Low-flow frequency characteristics were computed for the Mississippi River near Anoka, Minnesota and the Mississippi River at St. Paul, Minnesota.