By screening of a Leishmania infantum expression library with the serum from a dog affected with visceral leishmaniasis, a cDNA clone with sequence homology to the Hsp83 gene family was isolated. From analysis of the genomic distribution of the cDNA sequence, it was estimated that the L. infantum genome contains 7 Hsp83 genes tandemly organized. The full-length coding region of the Hsp83 gene located at the 5'-end of the cluster was determined. The deduced amino acid sequence of the L. infantum Hsp83 shows a high level of sequence identity with members of the Hsp83's protein family from other eukaryotic organisms. The complete protein (LiHsp83) and 4 subfragments (LiA1, LiB1, LiC1 and LiD1) were expressed in Escherichia coli as recombinant proteins and used as target antigens in FAST-ELISA assays against a collection of sera from dogs with visceral leishmaniasis. Ninety percent of the sera recognized the recombinant LiHsp83, indicating that L. infantum Hsp83 is a potent immunogen during canine leishmaniasis. Serological analysis of the recombinant subfragments identified the LiB1 subfragment, from amino acid 156 to 283, as the immunodominant region of the protein. This region, which is the less evolutionary conserved region of the protein, was recognized by 88% of the visceral leishmaniasis sera. The results suggest that L. infantum Hsp83 and particular protein subfragments may be useful in serodiagnostic assays for canine leishmaniasis.