In recent years, mediation has become increasingly popular as a means to resolve conflict. One important issue that arises out of the recent explosive growth in the practice of mediation is. what do mediators need to know in order to assist the parties in resolving their conflicts? This research attemtps to identify the determinants of mediator competence by examining the knowledge, skills and abilities of mediators in public sector labor relations. The research focuses on the core competencies requirements for mediators with the Federal Mediation and Conciliation Service and suggests which of the competencies may be applicable to mediation in other contexts.