The incidence of second molar impactions has not been adequately documented. Studies that have specifically investigated second molar impactions have reported incidences ranging from of 0.03% to 0.4%. In spite of this relatively low frequency in the general population, it seems that second molar impaction is not an uncommon occurrence in the orthodontic practice since the orthodontist is often the first to diagnose this condition in the adolescent patient. As a result, the orthodontist needs to be both cognizant of this potential problem and well equipped to handle the situation when it develops. The purpose of this article is to present the case of a patient who needed comprehensive orthodontic treatment, including rapid maxillary expansion and an uprighting of two impacted mandibular second molars and an impacted maxillary left canine. World J Orthod 2003;4:145–151.