Six days after transfer of eyed stage rainbow trout (Oncorhynchus mykiss) eggs into an incubator, egg mortality occurred during the winter of 2007. During the outbreak, approximately 30% of the eggs died. Rheocricotopus fuscipes (Kieffer, 1909) and Eukiefferiella claripennis (Lundbeck, 1898) (subfamily Orthocladiinae), Chironomid midge larvae were observed on the eggs by examining the eggs under the microscope. Histological sections of the infested eggs exhibited midge bite marks. This is the first report of Chironomid midges preying on fish eggs.