AbstractThis chapter examines mastitis in general terms, discusses the organisms involved namely Staphylococcus aureus, coagulase negative staphylococci, Streptococcus agalactiae, Streptococcus dysgalactiae, Mycoplasma, Coliforms, Escherichia coli, other coliforms, and Streptococcus uberis. This chapter also provides an overview of control measures.