Mastitis, or inflammation of the mammary gland, is the most costly disease affecting the dairy industry1. A variety of bacteria and fungi cause mastitis in dairy cattle; the disease-causing organisms are broadly classified as either environmental or contagious mastitis-causing organisms. The defining difference between the categories lies in the source of the organism which infects the cow: environmental mastitis organisms reside in the cow's environment, while contagious mastitis organisms are residents of the mammary gland itself and are transmitted predominantly by the milking machine and milker's hands. This report focuses on management of contagious mastitis due to the organism Streptococcus agalactiae.