Every arbitrator has had a scheduled arbitration hearing cancelled because the disputants have privately resolved the matter. This article identifies and examines those characteristics of grievance impasses that are associated with pre-arbitral dispute settlement — that is, settlement of a grievance dispute after submission to arbitration but before an award is issued — and those that are associated with arbitral dispute settlement — that is, settlement of a grievance dispute through issuance of an arbitration award. The study concludes that the primary determinant of pre-arbitral settlement is the degree of private, outside, legal representation.