Studies of vowel length acquisition indicate an initial stage in which phonological vowel length is random followed by a stage in which either long vowels (without codas) or short vowels and codas are produced. To determine whether this sequence of acquisition applies to a group of German-speaking children (three children aged 1;3–2;6), monosyllabic and disyllabic words were transcribed and acoustically analysed. The results did not support a stage in which vowel length was totally random. At the first time period (onset of word production to 1;7), one child's monosyllabic productions were governed by a bipositional constraint such that either long vowels, or short vowels and codas were produced. At the second (1;10 to 2;0) and third time periods (2;3 to 2;6), all three children produced target long vowels significantly longer than target short vowels. Transcription results indicated that children experienced more difficulty producing target long than short vowels. In the discussion, the findings are interpreted in terms of the representation of vowel length in children's grammars.