A sample of 62 cases of supernumerary teeth found in the lateral incisor area was selected and analysed. The great majority of these teeth were supplemental teeth, with deciduous precedents. Both teeth (the normal incisor and supernumerary) showed reduction in size as compared to the unaffected side. Differences were found between the mesial unit and the distal—the mesial being larger and having an incisor shape and the distal smaller and resembling a canine. Many of the pairs were similar to supernumerary teeth found in cleft lip and palate and there were also effects upon the other teeth particularly central incisors. Stigmata of cleft were observed in the alveolus, nasal floor and hard palate in a significant proportion of cases. It is concluded that supernumerary laterals arise by gemination or failure of development of normal odontogenic material. The anomaly fulfils the hypothetical criteria for a microform of cleft and may be the result of a minor error in embryonic fusion.