The lactose repressor protein interacts with DNA to perform a crucial role in the induction of lac enzyme synthesis in Escherichia coli. It serves as a primitive receptor for signal molecules (in this case sugars); in response to binding these sugars, a conformational change occurs in the repressor protein resulting in its dissociation from the DNA. This dissociation frees the DNA for synthesis of mRNA coding for the lac enzymes. An understanding of the process of induction requires elucidation of the molecular events which occur. Interaction of sugars with the repressor protein and the conformational change which results are essential points at which to begin an investigation. Fluorescence measurements provide a tool for uncovering information regarding macromolecular structure. By using native repressor fluorescence and by introducing fluorescent probes, both covalently and non-covalently, into the structure of the protein, it is possible to monitor the environment and changes in the environment surrounding these fluorophores. This type of information can be interpreted in terms of structural relationships within the protein and in terms of changes of such relationships. Since conformational changes are simply changes in structural relationships within a molecule, fluorescence measurements allow probes into an essential mechanism in the induction process: the conformational change of the lactose repressor. This type of understanding provides a basis for exploring other more complex systems.