The regulatory gene, alcR, of Aspergillus nidulans, encodes a protein that induces the expression of the alcA and aldA genes. The alcR gene is inducible, autoregulated, and subject to carbon catabolite repression. We report the complete nucleotide sequence of the alcR gene and its 5' and 3' non-coding regions. In the 5' flanking region of the alcR gene, several repeats and inverted repeats were found, and small sequence similarities were also found with the 5' flanking regions of the alcA and aldA genes. One intron of small size interrupts the open reading frame. The start point of transcription was mapped 50 nucleotides upstream from the putative start codon, and a sequence CAATG was found 5' to the polyadenylation site of the transcript that could play a role in selection of the polyadenylation site. The putative alcR-encoded protein was identified in vivo as an inducible polypeptide of 96 kDa in a transformant carrying multiple copies of the alcR gene.