Merlin, the Drosophila homologue of the human tumor suppressor gene Neurofibromatosis 2 (NF2), is required for the regulation of cell proliferation and differentiation. To better understand the cellular functions of the NF2 gene product, Merlin, recent work has concentrated on identifying proteins with which it interacts either physically or functionally. In this article, we describe genetic screens designed to isolate second-site modifiers of Merlin phenotypes from which we have identified five multiallelic complementation groups that modify both loss-of-function and dominant-negative Merlin phenotypes. Three of these groups, Group IIa/scribbler (also known as brakeless), Group IIc/blistered, and Group IId/net, are known genes, while two appear to be novel. In addition, two genes, Group IIa/scribbler and Group IIc/blistered, alter Merlin subcellular localization in epithelial and neuronal tissues, suggesting that they regulate Merlin trafficking or function. Furthermore, we show that mutations in scribbler and blistered display second-site noncomplementation with one another. These results suggest that Merlin, blistered, and scribbler function together in a common pathway to regulate Drosophila wing epithelial development.