The present article reviews the current understanding of regulation of cellulase gene transcription in Hypocrea jecorina (= Trichoderma reesei). Special emphasis is put on the mechanism of action of low molecular weight inducers of cellulase formation, the presence and role of recently identified transactivating proteins (Ace1, Ace2, Hap2/3/5), and the role of the carbon catabolite repressor Cre1. We also report on some recent genomic approaches towards understanding how cellulase inducers signal their presence to the transcriptional apparatus.