Analysis of 126 families comprising 205 patients with congenital glaucoma demonstrates that in Gypsies this disease follows the pattern of autosomal recessive inheritance with complete penetrance, while in the non-Gypsy population, its mode of inheritance is most probably multifactorial. In Gypsy patients with congenital glaucoma, the eyes are always bilaterally affected, the onset of the disease is in the prenatal period, and its course is rather severe. The population frequency of the disease is extremely high (among Gypsies), and the consanguinity rate among parents is as high as 41%. In non-Gypsy patients, 26.6% of all cases are only unilaterally affected, and the course of the disease is generally milder with a later onset. The population frequency in a non-Gypsy population is much lower, the consanguinity rate is not increased, and an excess of males (1.55:1) is significant.