In Daubert v. Merrell-Dow Pharmaceuticals, the Supreme Court established the federal trial court judge as an evidentiary gatekeeper. Under this new role, the Ninth and Eleventh Circuits created strict guidelines for the admission of scientific evidence.The new federal guidelines are sometimes more severe than the state standards within their circuits. A federal plaintiff otherwise able to admit evidence of causation in state court is barred from doing so in federal court, which leads to the case's dismissal on summary judgment. This outcome difference encourages eligible defendants to remove to federal courts, thus prejudicing some forum-state plaintiffs.This Note argues that the outcome differences between the Ninth and Eleventh Circuits and the state courts within their boundaries pose an Erie problem in diversity cases where the federal rule is stricter than the state rule.