Research suggests that widespread uncertainty over the scopes of issued patents creates significant costs for third-party firms and may decrease innovation. This Article addresses the scope uncertainty issue from a theoretical perspective by creating a model of patent claim scope uncertainty. It is often difficult for third parties to determine the legal coverage of issued patents. Scope underdetermination exists when the words of a patent claim are capable of a broad range of plausible scopes ex ante in light of the procedures for interpreting patents. Underdetermination creates uncertainty about claim coverage because a lay interpreter cannot know which interpretation will ultimately be elected and employed by a judge or jury in a patent infringement proceeding. This Article models this uncertainty problem by the set of interpretations that are plausible for a patent-claim element in light of constraints that restrict meaning, internal and external to the patent document. The model suggests generalizable properties against which we can critically evaluate patent interpretive rules and procedures. On this basis, the Article develops an approach to improving the ex ante scope precision of any given patent claim. The general approach is to reduce the set of interpretative scopes that patent claim words can plausibly obtain. By increasing explicit, scope-defining information in the public patent record, it is possible to improve scope precision by ex ante clarifying scope coverage and exclusion in foreseeable scope uncertainty scenarios.