The serratus posterior superior and inferior muscles are generally considered clinically insignificant muscles that, based on attachments, probably function in respiration. Interestingly, however, there is no evidence supporting a respiratory role for these muscles. In fact, some electromyographic data refute a respiratory function for these muscles. We suggest that the serratus posterior muscles function primarily in proprioception. Further, these muscles, especially the superior, have been implicated in myofascial pain syndromes and therefore may have greater clinical relevance than commonly attributed to them.