Spinning and tail chasing is the most common form of compulsive behavior shown by Bull Terriers. In a previous study, we defined the clinical signs, development, interaction with environmental, physiologic and psychological triggers, and response to pharmacological treatment in a sample population. Our pilot pedigree data for a large Bull Terrier family affected with tail chasing indicate that the disorder has a heritable component in this breed. Over the next two years, we will locate families of Bull Terriers affected with compulsive behavior. From this population, we will systematically collect detailed descriptive, medical historical and pedigree data for them and for two to three generations of relevant family members. We will collect blood samples from these affected Bull Terriers and their relatives, isolate the DNA and store the samples for genetic mapping studies to follow this project. The goal of these two projects is to identify chromosomal regions that contain susceptibility genes for compulsive behavior in Bull Terriers. Successful completion of both of these projects (DNA isolation and gene mapping) should have a significant impact on understanding the genetic basis of compulsive behavior in Bull Terriers. Our long-term goal is to use this information to contribute to the development of diagnostics, a treatment and a cure for the disease.