ENIt is widely thought that (i) Proto-Indo-European had *-mon-stem nominals formed by internal derivation from neuter *-men-stems and that (ii) these *-mon-stems were characterized by “amphikinetic” inflection, thus stressed full-grade of the root in their strong case forms (*R(é)-mon-). This paper challenges the latter claim, arguing that these forms instead had stem-final stress (*R(e)-món-). I adduce prosodic evidence in support of this alternative reconstruction from Lithuanian, Greek, Hittite, and above all Vedic Sanskrit, where the attested reflexes of these *-mon-stems consistently show stem-final stress. I then propose a new account of their root full-grade, which on this new reconstruction is phonologically irregular, since it surfaces in a pretonic syllable. I contend that this full-grade was synchronically transferred from their neuter *-men-stem bases. In this respect, internally derived *-mon-stems are shown to pattern morphophonologically with other reconstructible non-primary derivatives, which similarly acquire their root vocalism from their derivational bases. Keywords: Indo-European; phonology; morphology; word prosody; non-primary derivation; comparative reconstruction; language change. [From the publication]