BACKGROUND To detect the associated anomalies in patients with Axenfeld-Rieger syndrome is clinically important, because early treatment for such anomalies is crucial to both visual and systemic development. This study was conducted to clarify the associated anomalies in the syndrome. METHODS We evaluated 21 patients with Axenfeld-Rieger syndrome encountered at Nagoya City University Hospital over a 16-year period. Patients who presented with a prominent Schwalbe's line accompanying the iris strands were diagnosed as having Axenfeld-Rieger syndrome. RESULTS The series consisted of 9 males and 12 females, ranging in age from 1 month to 41 years, mean 15.4+/-12.7 (SD) years. The syndrome was bilateral in 17 cases and unilateral in 4 cases. Hypoplasia of the iris was observed in 10 eyes of 6 patients. The associated ocular anomalies included sclerocornea in 6 eyes of 3 patients, developmental glaucoma in 5 eyes of 3 patients, persistent pupillary membrane in 4 eyes of 2 patients, microphthalmos in 3 eyes of 2 patients, and typical iris coloboma in 1 eye. Of 10 eyes with hypoplasia of the iris, 5 exhibited glaucoma. The accompanying systemic anomalies included 9 cases of dental anomalies, 5 of facial anomalies, and 3 of Alagille syndrome. CONCLUSIONS All of the associated ocular and systemic anomalies appeared to arise from the maldevelopment of the neural crest cells. Patients with Axenfeld-Rieger syndrome should therefore be examined for the presence of anomalies in the tissues of neural crest origin. Patients with hypoplasia of the iris should be checked for glaucoma.