Expression of 10 CYP orthologs (Families 1-3) in developing mouse conceptus is constitutive. These forms have specific temporal and spatial expression. Studies on CYP1B1 indicate its requirement for normal eye development, both in human and mouse. The distribution of the enzyme in the mouse eye is in three regions, which may reflect three different, perhaps equally important, functions in this organ. Its presence in the inner ciliary and lens epithelia appears to be necessary for normal development of the trabecular meshwork and its function in regulating intraocular pressure. Its expression in the retinal ganglion and inner nuclear layers may reflect a role in maintenance of the visual cycle. Its expression in the corneal epithelium may indicate a function in metabolism of environmental xenobiotics.