This specially curated collection features four reviews of current and key research on mastitis in dairy cattle. The first chapter reviews the indicators of mastitis and the contagious and environmental pathogens which cause it. It then discusses how mastitis can be managed and controlled on dairy farms, including consideration of dry cow therapy and the use of antibiotics. The second chapter examines the impact of clinical and subclinical mastitis in cows on milk quality, and provides a detailed account of indicators of mastitis. It describes the impact of mastitis on milk composition and quality, addressing its effect on the protein, fat, lactose and iron content of milk. The third chapter reviews advances in dairy cattle breeding to improve resistance to mastitis. It includes sections on both conventional and new phenotypes for improving resistance to clinical mastitis and concludes with a section on increasing rates of genetic gain through genomic selection. The final chapter considers recent research on the prevalence and development of antimicrobial resistance in mastitis pathogens. It shows how consistent diagnostic protocols and recording systems, attention to medical history, appropriate choice of antibiotics and control of treatment duration can all contribute to minimizing unnecessary use of antimicrobials and promoting effective treatment of mastitis.