The eye of the adult Drosophila comprises 800 unit eyes known as ommatidia. Each ommatidium is composed of 8 photoreceptors and 12 accessory cells. Ommatidia are organized into dorsal and ventral chiral forms that are determined by their position relative to an equator that bifurcates the adult eye. This midline is established in larval development through the juxtaposition of independent dorsal and ventral compartments specified by differentially expressed and antagonistic gene networks. Here, I show that the Pax6 transcription factor, eyeless (ey), has a role in mediating the establishment and maintenance of the early DV patterning of the Drosophila eye. Flies harboring mutations in ey have either small or no eyes. I have examined the developing and adult ey mutants and have evidence that D/V patterning is disrupted. The developing eye shows an increase in the expression pattern of the dorsal selector gene mirr which suggests ventral eye tissue is reduced or lost. Consistently, the adult eye of ey mutants is composed solely of ommatidia of dorsal chirality. Additionally, the dorsal selector gene wg and the dorsal head capsule selector otd also show increased spatial expression in ey mutants, supporting the hypothesis that the loss of ey disrupts D/V patterning. The midline, which can be visualized by the expression of a fj-lacZ reporter, is shifted in accordance with the increased expression pattern of dorsal selector genes. Together, these data suggest that the loss of ey affects the formation of dorsal and ventral compartments in the developing eye. This represents a new role for Pax6 in eye development.