Domestic dog breeds are an important resource for mapping of genetic disorders, with relevance to other species including humans. Both conventional association analysis of a phenotype within members of a single breed, and comparison of allele frequencies between breeds that differ in trait susceptibility, have been demonstrated to be particularly efficient, because of the small effective population size of many breeds. We present preliminary results from both these types of analysis using 96 German Shepherds, 96 Golden Retrievers, 48 Miniature Bull Terriers, 96 Pugs, and 60 WHW Terriers genotyped using the Illumina Canine GWAS array V2 to date in a case-control study of hemangiosarcoma. The first two breeds have higher rates of cancer in general, and of hemangiosarcoma in particular.