DNA binding and transcriptional activation by basic region leucine zipper (bZIP) proteins can be enhanced by accessory factors. In the past year, three accessory factor-bZIP-DNA complexes have been investigated extensively. Experiments have probed the effect of accessory factors on bZIP-DNA specificity, the residues that participate in stabilizing these complexes, the contribution of DNA conformation to accessory factor-bZlP interactions, and the relative stabilization of bZIP dimerization and DNA binding by accessary factors.