A recombinant clone encoding for the human desmin gene (des) has been isolated and characterized and its complete nucleotide sequence has been determined. The 8.4-kb gene has nine exons separated by introns ranging in size from 0.1-2.2 kb. Comparison of the human des gene with that of the hamster has shown that there is a full correspondence in position, size and sequence of the exons. There are eight introns in both the human and the hamster des genes. Although the nucleotide sequence of the introns reveals a large divergence, splice junction sequence signals are conserved. A particularly striking feature of the human des gene is the 1.2-kb repetitive sequence found in the introns. These sequences all belong to the human AluI family. When the 5'- and 3'-untranslated regions of the human vim and des genes were compared it was found that there was a 16-mer consensus element similar to that described by Quax et al. [Cell 43 (1985) 327-338] for the hamster and an 11-bp sequence with homology to the distal regulatory sequence of human and mouse alpha-cardiac actin-coding genes [Minty and Kedes, Mol. Cell. Biol. 6 (1986) 2125-2136] in the 5'-flanking region. The 3'-untranslated region of the human des gene was found to be conserved when compared to the hamster des gene. Only one species of desmin RNA of 2.2 kb was found in human striated and smooth muscle both in vivo and in vitro.