Utterance-final lengthening in Northern Finnish was investigated using tightly controlled laboratory materials, with particular focus on its interaction with the language’s single (short) vs. double (long) vowel distinction. Like many other languages, Finnish exhibited utterance-final lengthening, which extended to the stressed, penultimate syllable of disyllabic words. The estimate of magnitudes of lengthening on final vowels varied greatly, however, depending on the treatment of the utterance-final breathy/voiceless portion of the vowel. In addition, vowel quantity interacted with lengthening in an intricate manner. We argue that the interaction between quantity and lengthening is motivated by the maintenance of quantity distinction.