The main purpose of this dissertation is to study the use of the ýr-rune in Scandinavian runic inscriptions. The rune, in the shapes m (older) and z (younger), originally denoted /R/, i.e. palatal r, which eventually merged with /r/. The time of the merger and the relationship between /R/ och /r/ has traditionally been regarded as uncertain, and how /R/ was phonetically realized has been a matter of debate. Based on the available information, it is suggested that /R/ could be described as a palatal fricative. The main difference between /R/ och /r/ could, therefore, have been that the former was realized as a fricative, the latter as a trill/approximant.
The use of the ýr-rune is unproblematic in the inscriptions carved in the older runic alphabet: it is, with one uncertain exception, consistently used for etymological /R/. During the Viking Age, a significant change takes place, manifested by the gradual and eventually complete dominance of the reið-rune, r. We are not, however, dealing with an irregular alternation between the two runes, since r used for original /R/ is rather common, whereas z used for original /r/ is most uncommon.
The transition /R/ > /r/ first occurs in position after dental and alveolar consonants, then after other consonants and finally after vowels. A regional difference is also clear: the use of the ýr-rune to denote /R/ dies out much earlier in Western Scandinavia than in Eastern Scandinavia.
The ýr-rune was also used to denote a number of vowels, in Western Scandinavia /y/, in Eastern Scandinavia several different vowels, probably all unrounded: /e(:)/, /i(:)/ and /æ(:)/. The use of the ýr-rune for /y/ in Eastern Scandinavia is first recorded in the mediaeval inscriptions.
The denotation of older /R/ in Viking Age inscriptions shows considerable intra- and extralinguistic variation, aspects which receive attention in the present work. The ýr-rune continues to denote older /R/ during the early Middle Ages, primarily in Gotland, occasionally also in Denmark, Småland, Södermanland, Västergötland and Öland; the conclusion drawn is that /R/ still existed at least into the 13th century.