This diploma thesis deals with different aspects of witness evidence - in particular with evidence provided by witnesses of fact - in arbitration proceedings. Special emphasis is put on the comparison between arbitration and litigation proceedings as well as on the differences between civil and common law jurisdictions. The first chapter provides a general overview of various forms of evidence in arbitration proceedings and describes the historical development of witness evidence in arbitration. Following this, the requirements for giving witness testimony are laid out, with a detailed elaboration on the duties and rights of witnesses. Furthermore, a description takes place on the possible consequences in case of refusal to give testimony. The next chapter deals with different forms of witness testimony, including an overview of traditional forms, such as written and oral evidence, as well as modern newly developed methods of evidence taking, such as witness conferencing. Subsequently, the reader will gain insight in the interplay of arbitral tribunals and state courts regarding the procedure of providing legal assistance to arbitral tribunals in evidentiary proceedings. The fifth chapter is dedicated to the evaluation of witness evidence, including a comparative analysis of different forms of evidence. Lastly, aspects of best practice and thoughts on future developments are addressed. The aim of this thesis is to describe the role of witnesses of fact in arbitration in detail, taking into account differences between various jurisdictions and litigation proceedings, especially in Austria.