Mastitis is one of the main health issues in dairy production. The losses are not only economic, but also issues such as animal health and welfare, milk quality, antibiotic usage and the image of the dairy sector are important reasons to focus on mastitis control. Accordingly, mastitis is a topic that is well-studied worldwide. Although the scope of the studies may vary from the smallest unit, the gene, to the largest unit, a whole country, the final goal is to control mastitis more effectively. Effective mastitis control is based on knowledge from a wide range of fields, like infectious pressure, milking procedures, resistance, detection, diagnosis and treatment. However, science alone is not enough. To ensure effective mastitis control, research needs to be inspired by, and implemented in, dairy farming practice. This demands cooperation and communication between scientists, veterinarians, extension specialists and dairy farmers worldwide. This book gives the state of the art of mastitis research internationally. The contributions reflect not only current knowledge of mastitis control, but also provide ideas for effective mastitis control in practice.