Hedgehog (Hh) signaling controls a multitude of developmental processes in Drosophila and other organisms, including humans. This is accomplished through carefully regulated expression and transport of Hh signaling molecules, followed by transduction of the Hh signal and induction of transcriptional responses that alter cell fates or cell proliferation. Our overall objective is to understand the Hh signal transduction process principally by studying Hh signaling in developing Drosophila wing discs, where detailed and incisive genetic tests are possible.