During the last 15 years wool fibre analyses have been made of Danish archaeological textiles dated from the Bronze to the Viking Ages (c.1800 BC - AD 1050). Because of the extraordinary preservation of these textiles the material is ideal for making qualified interpretations regarding wool fibre development and processing. The work has lead to an elaboration of the known methods used so far for classifying prehistoric wool. The methodology is explained and may be applied for similar studies. The fibre quality in the different archaeological periods is presented and changes in the wool fibres are defined. The principles for the processing of the wool are assessed for each period. In this way new and more specific knowledge has been acquired in regards to wool fibre development and the work, desires and choices of prehistoric textile crafts people.