Summary: Over the last three years, GAO has reviewed the development of the M1 tank, concentrating on: (1) operational and developmental testing, particularly reliability, maintainability, and logistical supportability of the M1; (2) the Army's efforts to improve the M1 power train's durability; and (3) the possible consequences of large-scale M1 prduction before its durability problems are resolved. Tests have demonstrated the tank's excellence in most of its critical performance areas. However, some of this capability could be lost due to problems with the power train. GAO has felt that the M1 should be produced in limited quantities until the power train could be improved. Otherwise, there is a risk of building up an inventory of M1 tanks with power train components that may need frequent maintenance or replacement. The Army would like to accept the tank with its current capability while embarking on an improvement program. Congress provided funds in the 1982 Defense Appropriation Act for putting the tank into full production. The Army is planning to test M1 tanks outfitted with diesel engines and turbine engines. GAO suggests that a cost and performance comparison of the two engines might be in order. However, the Army is not inclined to do this because over 3,000 M1 tanks will have been produced before a diesel engine could meet Army acceptance tests. The reliability of test equipment, the adequacy and completeness of training manuals, the tank's high fuel consumption, and the maintenance burden were some of the supportability areas that obviously needed improvement when GAO reviewed the program in 1981. The Army has made some progress in these areas. It has been running a successful training program with the first tank units delivered to Europe. However, GAO has not made an assessment of this program in recent months. Testing later this year should furnish some answers as to how far the Army has progressed in solving the problems.