Vowel reduction and deletion are prominent correlates of stress in German and some preliminary investigations have suggested that this constitutes an area of difficulty for non-native speakers. This paper explores the production of vowels in unstressed syllables by learners of German, focusing especially on the acoustic properties duration and formant structure. It is shown that the realization of unstressed vowels in non-native German is influenced by the speakers’ native language (L1), but not by speaking style.