The BAH (Bromo-adjacent homology) domain is a domain first identified in the vertebrate polybromo protein, a protein present in a large nuclear complex. Polybromo has two BAH domains, six bromodomains and an HMG-box. The BAH domain has been identified in a number of proteins involved in gene transcription and repression and is likely to be involved in protein-protein interactions. Polybromo resembles two related proteins in yeast, the Rsc1 and Rsc2 proteins, both having a BAH domain and two bromodomains as well as a DNA binding motif, the AT -hook. The Rsc1 and 2 proteins are components of the RSC (remodelling the structure of chromatin) complex and are required for transcriptional control. In this paper we review recent data on the function of the BAH and bromodomains in relation to polybromo and the Rsc proteins.