The BET proteins are a novel class of transcriptional regulators whose members can be found in animals, plants and fungi. Founding members are Human RING3, Drosophila Fsh and yeast Bdf1p. BET proteins are distinguished by an N-terminal bromodomain or bromodomains and an ET domain. As predicted by the presence of the bromodomain(s), these proteins have been found to be associated with chromatin. The poorly characterized ET domain functions as a protein-protein interaction motif and may be part of a serine-kinase activity. Other regions ("modular domains"), which are conserved only in certain BET proteins, are likely to provide sub-family specific functions. Genetic, biochemical and molecular techniques have implicated BET proteins in functions as diverse as meiosis, cell cycle control and homeosis. The data suggest that BET proteins may modulate chromatin structure and affect transcription via a sequence-independent mechanism. This review will attempt to summarize current research on BET proteins and envision where future research is likely to lead.