Studies of isotopes in groundwater using 14C, 2H (deuterium) and 18O have provided significant insight into the paleoclimate of middle and late Wisconsin age in a typical arid environment of southern Nevada, the west-central Amargosa Desert. Evidence indicates that recharge probably was through infiltration of runoff in paleostream channels and that this runoff was important only from ??? 17,000 to ??? 10,000 yr. B.P. Mean annual temperature at 17,000 yr. B.P. was ??? 8??C less than present mean annual temperature; some summer moisture was effective in recharge. Winter (October-May) temperature at ??? 10,000 yr. B.P. was ??? 1??C less than present; summer moisture did not contribute to recharge. ?? 1986.