An analysis of English Expletive Infixation (as in fan-fuckin-tastic) in terms of a metrical theory of prosody is presented. It is shown that the major environment for Expletive Infixation—immediately before a stressed syllable—follows from independently motivated characteristics of this theory. Further support for this metrical theory is adduced from infixation in words with dactylic stress alternation and with internal stress-neutral junctures, and from the subordination of stress in forms after infixation.