This paper presents parts of the results of the first stage in the phonetic documentation of Fering, a dialect of North Frisian. Descriptions of Fering indicate that it has a large vowel inventory (15 monophthongs, 7 diphthongs, and 3 triphthongs). Ten older male native speakers were recorded, producing the vowel and consonant inventory at different speaking rates, in different phonetic contexts, and in different speaking styles. The results of the acoustic analyses of the vowels of Fering throw light on the questions of a) how the vowel space is exploited in Fering, b) how Fering differentiates its large vowel inventory, c) to what extent consonant–vowel coarticulation affects the acoustic differentiation of vowel categories, and d) to what extent the implementation of the long–short vowel contrasts is affected by speaking rate. The results also provide a more accurate description of the vowel system of an endangered language than do previous auditory accounts.