Ten-a is one of the two Drosophila proteins that belong to the Ten M protein family. This protein is a type Ⅱ transmembrane protein and is expressed mainly in the embryonic CNS, in the larval eye imaginal disc and in the compound eye of the pupa. Here,we investigate the role of ten-a during development of the compound eye by using the Gal4/UAS system to induce ten-a overexpression in the developing eye. We found that overexpression of ten-a can perturb eye development during all stages examined. In an early stage, overexpression of ten-a in eye primordial cells caused small and rough eyes and interfered with photoreceptor cell recruitment, resulting in some ommatidia having fewer or extra photoreceptor cells. Conversely, ten-a overexpression during ommatidial formation caused severe eye defects due to absence of many cellular components. Interestingly,overexpression of ten-a in the late stage developing ommatidial cluster affected the number of pigment cells, caused cone cells proliferation in many ommatidia, and caused some photoreceptor cell defects. These results suggest that ten-a may be a novel gene required for normal eye morphogenesis.