Transmigration is the pre-eruptive intrabony migration of a tooth across the midline. This rare phenomenon, the etiology of which is unknown, is usually seen in canines. Two cases of transmigration in the mandibular canines are reported; one shows the transposition of a maxillary canine and premolar. Familial occurence of this phenomenon and a 5-year follow-up showing a change in the inclination of the impacted tooth are outlined. Keywords: familial, impaction, mandibular canine, transmigration