Regional odontodysplasia (RO) is a rare dental anomaly involving both dentitions, mostly teeth of one quadrant. The characteristic findings are discolored soft teeth accompanied by gingivitis, swelling or abscess. Enamel and dentin are hypomineralised and hypoplastic, so that the 'ghost teeth' appear shadowy in radiographs with wide pulp chambers. The etiology is unknown. Epidemiological data is rare; 138 cases of RO have been published to date and reports on ultrastructure are few. An analysis of published cases of RO in the international literature is presented. The sex ratio of females to males was 1.7:1. The age at the time of diagnosis ranged between 4 and 23 years. The maxilla was more often affected (maxilla to mandible ratio 1.6:1). In 67 patients the deciduous and permanent dentitions were affected (47.1%). In 129 cases, affected teeth lay side by side. Missing tooth development was observed in 10.7%. Failure of tooth eruption of RO teeth occurred in 39.7%. In addition, four cases with RO which were collected over a period of more than 25 years are presented. Ultrastructural findings of one specimen are demonstrated.