We describe here the fortuitous cloning of a putative transcription factor gene (MTF1) from the dimorphic fungus Mucor circinelloides. Sequence analysis of MTF1 revealed an open reading frame (ORF) of 1059 nucleotides encoding a protein of M(r) 39601. The deduced amino acid sequence from the ORF imparts two glutamine-rich stretches which are homologous to a number of transcription factors characterized previously from various organisms. A Southern blot analysis of Mucor genomic DNA digested with different restriction endonucleases and probed with the 1.9 kb EcoR1 fragment of the putative transcription factor gene shows a single copy number of the the gene. Northern analysis during morphogenetic changes in Mucor suggested constitutive expression of the gene.