In recent years, public attention has focused on the need for affordable prescription drugs. Although Congress has recently enacted a Medicare Prescription Drug Plan, many private citizens and state and local governments continue to reimport prescription drugs from Canada to take advantage of the lower drug prices available in Canada. Many pharmaceutical companies have responded to this phenomenon by cutting off supplies of their drugs to Canadian pharmacies engaging in reituportation. As a result, some state and local governments have initiated litigation alleging state antitrust violations. This Note addresses one of the first questions raised in U.S. antitrust litigation under the Rule of Reason—the definition of the geographic market. First, this Note surveys the current caselaw standard and the academic approaches to geographic market definition. This Note then applies these approaches, concluding that Canada may be included in any geographic market when addressing the legality of reimportation in an antitrust context.