Pet dogs are special because they share both our environment and the same diseases as humans, such as autoimmune diseases, neurological diseases, cardiovascular disease and cancer. On top of this, there has been very strong selection in dogs for morphological traits and behavior, suggesting that rare variants with strong effect may have become more common in certain breeds, leading to diseases. The recent creation of breeds (in the last 200 years) also means that haplotype blocks are long within breed and short across breeds. This allows for a mapping strategy where first high-risk breeds are used to find the rough locations of disease mutation, and then other breeds are added in to fine-map the region to find the causative mutation. Due to this, dogs are excellent models for human disease and we have identified disease associated variants in osteosarcoma, obsessive compulsive disorder and several immunological diseases.