Abstract: Cleft lip repair plays a prominent role in contemporary plastic surgery.  Although the last century has seen remarkable progress in cleft reconstruction, a thorough description of musculature underlying the upper lip and associated structures remains obscure and highly debatable.  In order to effectively restore local muscular equilibrium and provide optimal cosmetic outcome, a thorough understanding of musculature underlying the upper lip, philtrum, and nasal floor is imperative.  Fine anatomic dissection of the upper lip, philtrum, and nasal floor in 5 adult cadavers provided several key insights.  Most strikingly, tissues of the orbicularis oris from one side decussated immediately beneath the philtral groove before inserting into the skin of the contralateral philtral groove.  Although the philtral groove immediately overlay this complex decussation, a relative paucity of muscular insertion to this area was readily apparent.  At more inferior philtral levels, the levator labii superioris descended medially to insert along the philtral column and vermilion border.   It is the complex anatomic relationship of this area which we feel is most responsible for the lateralization of nasal and midline cheek tissue in the setting of cleft lip/palate.  Based on our experience, we suspect that cleft abnormalities are associated with a much more lateral insertion of this intersection.  Here we present our findings from the gross dissection and anatomic study of adult peri-oral musculature, as well discuss these findings in the context of cleft lip and palate.