Several researchers have noted that intervocalic consonants are unusually long in Navajo (Sapir & Hoijer 1967, Young & Morgan 1987, McDonough & Ladefoged 1993). This paper explores intervocalic consonant duration in the Lheidli dialect of Dakelh (Carrier) in order to determine whether the long intervocalic consonants found in Navajo are characteristic of other Athabaskan languages as well. It is shown that Lheidli intervocalic consonants are substantially longer overall than (a) consonants in other positions within Lheidli, (b) vowels within Lheidli, and (c) singletons and geminates in other non-Athabaskan languages. Furthermore, intervocalic consonant duration is at least in part a function of morphological structure, with intervocalic consonants lengthening to signal a stem morpheme boundary. The data presented here provide new evidence for the existence of a language-specific phonetic component of grammar as well as for the interaction between phonetics and morphology.