The vowel quality of filler particles (FP) is studied for 24 speakers of German who produced 666 instances of vocalic (äh) and vocalic-nasal forms (ähm) in spontaneous dialogues. The FP vowel quality is compared to reference vowels of a word list as well as to phonologically and graphematically similarly constructed lexical syllables. Filler particles show a complete overlap with the reference vowels [œ] and [5], but overlap only partially with [E] and [@].