Do loanword adaptations apply on a phonological or a phonetic level? This study addresses this issue by investigating the adaptation of German and French loanwords and proper names with front rounded vowels into Japanese. The adaptation forms of front rounded vowels are analysed from a phonological and a phonetic perspective. Both the phonological and the phonetic analysis can account for part of the data, but neither alone is able to account for all the adaptation forms of German and French front rounded vowels in Japanese. It is shown that adaptations are complex processes determined by a variety of factors such as perception, knowledge of the source language, and written forms. Furthermore, it is shown that socio-linguistic factors have a major impact on adaptation processes.