In the past year, the crystal structure of a dimeric version of the Escherichia coli Lac repressor bound to operator DNA was determined at 2.6 Angstrom resolution, providing a closer View of the operator-bound conformation of the repressor. Refined NMR studies of the DNA-binding portion of the repressor complexed to operator DNA have revealed further details of the unique DNA-binding interactions of the repressor. The structural studies have been complemented by continued biochemical studies, with the overall goal of understanding the mechanism of allosteric regulation.