A 3-isopropylmalate dehydrogenase (3-IPMD) gene was cloned from Kluyveromyces fragilis. pJK104 could complement Escherichia coli leuB and Saccharomyces cerevisiae leu2 auxotrophs. The coding region was subcloned and the nucleotide sequence was determined. A 1.8 Kb EcoRI/SphI fragment of pJK104 subcloned in pUC18 could still complement the leuB mutation. An open reading frame of 1164 bp that corresponds to a polypeptide of 387 amino acids was found in the cloned fragment. The homology between the 3-isopropylmalate dehydrogenase of S. cerevisiae and that of K. fragilis was 68.13％ in nucleotides.