The present study investigates the phonology of glides in Middle High German. On the basis of surface contrasts between prevocalic nuclear glides in syllable-final position ([VG.V]) and postvocalic glides in onset position ([V.GV]), it is argued that the latter were underlying glides (e.g. the /w/ in [le.wə] ‘lion’) and that the former were glides derived from vowels (e.g. the offglide [o̯] in the diphthong [uo̯] from /uo/). Underlying glides are argued to be [+consonantal], while nuclear glides ‒ like the vowels from which they derive ‒ are [‒consonantal].The analysis of Middle High German bears on several debates involving glides in the theoretical literature. First, a treatment with an underlying glide in /VGV/ cannot be reanalyzed by treating the vowels as peaks (e.g. Harris & Kaisse 1999 for Argentinian Spanish). Second, the treatment of underlying glides as [+consonantal] is to be preferred over alternatives which analyze those sounds as [‒vocalic] (e.g. Nevins & Chitoran 2008 for several languages). Third, an analysis of nuclear structure is adopted (from Harris & Kaisse 1999) which enables one to interpret which element in a complex nucleus is the peak and which is the nonpeak without stipulation. Fourth, the contrastive syllabification of surface glides (i.e. [VG.V] vs. [V.GV]) is shown to be a diagnostic of underlying glide languages that has not been discussed in the literature to date.