GAO reported on the status of the land-based Intercontinental Ballistic Missile (ICBM) Modernization Program, specifically: (1) the deployment of 50 Peacekeeper missiles in existing Minuteman silos; (2) research to determine a survivable basing mode for 50 additional Peacekeeper missiles or other missiles; and (3) the development of a small, single-warhead ICBM. GAO found that: (1) the Department of Defense (DOD) began studies of a single-warhead small ICBM weighing 37,000 pounds because of a need for increased range and payload flexibility; (2) DOD is studying missile quantities, basing characteristics, and other factors that influence ICBM program costs; (3) the estimated life-cycle cost of 500 such missiles is between $44.8 billion and $52.1 billion; (4) preliminary testing on the missile launcher's ability to adequately survive a nuclear attack is promising; (5) DOD expects to select suitable land for basing by December 1986; and (6) DOD has not specified the ICBM survivability level or whether that level is achievable. GAO also found that: (1) the Air Force is studying eight alternative basing concepts to allow deployment of 50 additional Peacekeeper missiles; (2) the automated total life-cycle cost for the Peacekeeper program is $21 billion; (3) the life-cycle cost estimates for a combined force of 500 small ICBM's and 100 Peacekeepers range from $73 billion to $109 billion; (4) the cost estimate for alternative ICBM forces is not available; (5) DOD is studying the feasibility of developing mobile missiles weighing up to 75,000 pounds with the capability to carry two or three warheads; and (6) Congress linked the Peacekeeper deployment schedule to the small ICBM system.