Over the last 1,300 years Europe and the Islamic world have confronted each other. The dynamic and even tense relationship between them has caused cultural interchanges which are clearly marked on both. The present study focuses on portable Islamic objects in European church treasuries and, therefore, belongs to the large field of research of East-West interaction. A corpus of Islamic artefacts still or formerly in the possession of the medieval church treasuries of Europe has not as yet been the subject of wholly comprehensive examination, and the present study is intended to contribute to this as yet largely unexplored field. The scope of this study is confined to the Middle Ages, namely from the mid 7^th century until ca. 1300, with the exception of medieval Spain which is dealt with up to the fall of the Nasrids in 1492. It examines East-West interactions only from one side of the coin, namely Islam in the West, and is restricted to the Latin West. Unlike former approaches, this study does not discuss the impact or the influence that these artefacts had on the art of the West, but tries to answer how Islamic artefacts reached the Latin West and what the attitude towards them in the ecclesiastical sphere was. The body of the thesis is divided into three main parts. In the first part the principal different 'routes' by which Islamic objects reached the Latin West are examined. The objects are classified into five groups. The first chapter deals with Islamic vessels which were brought by pilgrims as souvenirs from the Near East. The second one focuses on the exchange of royal presents. The third one examines the accounts referring to the dispersion of the Fatimid treasury.