There is contradictory evidence for the prosodic structure of Russian prepositions and prefixes. While most criteria suggest that both prepositions and prefixes form single phonological words with their hosts, the vowel-Ø alternation known as yer realization falls out of line with other diagnostics, in that it seems to apply differently to prepositions and prefixes. In this paper I resolve the apparent paradox by taking a closer look at the complex and variable data on yer realization with prepositions, which has previously not been examined. I use the intricate phonotactic, syntactic, and lexical factors that affect yer realization to infer the correct prosodic representation of the structures. The proposed representation is independently corroborated by the behavior of an unrelated rule of stress retraction, which is subject to a set of restrictions that closely mirror those on yer realization.