Genetic approaches are beginning to provide valuable insights into the function of specific gene products in olfaction. Analysis of Drosophila mutants that affect olfactory responses are defining components of the olfactory signaling mechanisms. Mutations in the genes paralytic and Scutoid cause olfactory defects, as do mutations in genes encoding products that mediate visual responses. In addition, members of the family of invertebrate odorant-binding proteins have been identified in Drosophila and may play an important role in the olfactory process.