Many of the major procurement activities and programs of the Department of Defense (DoD) are experiencing cost growth costing the United States (U.S) government money. The purpose of this research was to develop an empirical model in order to explain cost overruns in the DoD major procurement activities and programs.Specifically, this thesis sought to discover relationships between cost overruns inweapon systems programs and factors that the DoD cannot control, factors that originatefrom the political nature of the defense acquisition process. The model describes how thepolitical and legislative balances of power between the parties of the Congress, thechange of the purchase habits of the DoD from production contracts to service contracts, and the spreading of defense manufacturing capacity across the states of the U.S arerelated to cost overruns in defense programs.This research effort studied 193 major weapon system programs from 1970 to2002 using Ordinary Least Square regression techniques. Results show that a DemocraticPresident leads to a reduction in cost growth, while control of both houses of Congress byone party, or control of the Senate and the office of the President by one party causes costincreases