AbstractPrevious studies of the tooth and dental arch dimensions in twins have suggested that the size and form of the dentition is more under genetic control than the size and form of the dental arch. A study of dentition and dental arch was carried out on three sets of same‐sex triplets, two sets being monozygotic and one set dizygotic. No significant differences were found in the dental arch dimensions in any set of the triplets. The tooth dimensions showed no significant differenes in the monozygotic triplet sets or in the monozygotic pair from the dizygotic triplet set, but showed significant differences between the monozygotic pair and the third member of the dizygotic set. This confirms the data obtained from twin studies.