HMGA1 nonhistone proteins are reported to participate in various cellular processes including regulation of inducible gene transcription, integration of retroviruses into chromosomes, and the induction of neoplastic transformation and promotion of metastatic progression of cancer cells. Overexpression of HMGA1 was shown to be characteristic for various malignant tumors, suggesting a relation between the neoplastic phenotype and a high titer of the protein. Also chromosomal aberrations affecting the human HMGA1 gene at 6p21 were described in several tumors, e.g., uterine leiomyomas, pulmonary chondroid hamartomas, and follicular thyroid adenomas. We characterize the molecular structure of the canine HMGA1 cDNA, its splice variants, and predicted proteins HMGA1a and HMGA1b. Furthermore, we compared the CDS of both splice variants for 12 different breeds, screened them for SNPs, characterised a basic expression pattern, and mapped the gene via FISH. Additionally, we compared the known human, canine, murine, rat, hamster, bovine, pig, Xenopus, and chicken HMGA1 transcripts.