A patient with ring chromosome 6 had most of the manifestations previously reported in this syndrome and also had albinoid fundi and unilateral aniridia, findings not previously described. In most peripheral leukocyte metaphases analyzed, one chromosome 6 was replaced by a monocentric ring chromosome with deletion of the 6p and 6q. Fifteen other patients with a ring chromosome 6 have been reported. The most frequent findings were mental retardation, prenatal and postnatal failure, epicanthal folds, flat nasal bridge, short neck, apparently low-set and/or malformed ears, microphthalmia, and micrognathia. Studies of coagulation Factors XII and XIII and of the P blood group for possible assignment on distal 6p and 6q did not provide evidence for localization of the genes for these factors on the pter----p24 part of chromosome 6.