The U.S. Air Force's poor air combat results in Vietnam prompted more realistic training programs to improve our fighter pilots' air combat effectiveness. The establishment of dissimilar air combat training conducted by a professional "aggressor" force has given Tactical Air Command fighter pilots the hostile environment and realistic adversary that were lacking in a predominantly F-4 fighter force. This thesis examined the need for F-5E Aggressor Squadrons to perform this dissimilar air combat role now that the F-l5 and F-l6 fighter aircraft are in production. The evaluation of Aggressor Squadron operations encompassed both training and cost analyses. The training effectiveness was examined by analyzing Air Force and Navy air combat results in Southeast Asia with and without an Aggressor DACT program and projecting the outcome to a future conflict. The operating costs of the F-4, F-5E, F-l5, and F-l6 were investigated to determine the most economical vehicle to provide Aggressor training. The general conclusion of this thesis is that the F-5E Aggressor Squadrons should continue as the focal point of enemy tactics, weapon systems and philosophy. Recommendations to improve air combat training and overall tactical force readiness are presented for consideration.