The independent effect of the contraction of various facial mimetic muscles on the nasolabial fold was defined through study of cadaver dissections. The four major lip elevator muscles were identified and the effect of traction of these muscles on the nasolabial fold was studied. This study identified the levator alae muscle (levator labii superioris alaeque nasi) as the primary facial muscle responsible for creating the medial nasolabial fold. The levator labii superioris muscle was found to define the middle nasolabial fold. These two facial muscles may be significant in the etiology of the prominent nasolabial fold that occurs with aging.