The authors report on two siblings with severe malformations of the eyes. The 16-year-old girl has bilateral microphthalmus with aplasia of the right optic nerve and a Dandy-Walker cyst of the cerebellum. The right eye has no optic disk or retinal vessels. Her 13-year-old brother has unilateral aplasia of the optic nerve with cryptophthalmus and contralateral microphthalmus. In a computer tomography examination no optic nerve could be demonstrated on the left. The presence of an oculocerebral dysplasia in a brother and sister with healthy parents suggest an autosomal-recessive mode of inheritance of the aplasia of the optic nerve with microphthalmus and/or cryptophthalmus.