SUMMARY. Staphylococcus aureus and various coagulase-negative staphylococci were isolated from turkeys with staphylococcosis. Virulent S. aureus adhered well (averaged more than 100 bacteria per tissue cell) in vitro to cells from tissues of the respiratory tract but did not adhere well (averaged fewer than 12 bacteria per tissue cell) to cells from tissues of the alimentary tract. Some avirulent coagulase-negative staphylococci also adhered well to cells from the respiratory tissues. Lungs and livers of turkeys became colonized with virulent S. aureus following experimental aerosol exposure. Tracheas, livers, and hock joints of some market-age turkeys were naturally colonized with S. aureus and various species of coagulase-negative staphylococci. RESUMEN. Estafilococosis en pavos. 1. Puerta de entrada y colonizaci6n de tejidos. Se aisl6 Staphylococcus aureus y varios estafilococos coagulasa negativos a partir de pavos con estafilococosis. In vitro, un elevado numero de cepas virulentas de S. aureus se adhirieron a las celulas obtenidas de tejidos del tracto respiratorio pero no asi a las celulas obtenidas de los tejidos del tracto alimentario. Unas pocas cepas de estafilococos coagulasa negativas tambien mostraron una buena adherencia a las c6lulas de los tejidos respiratorios. Los pulmones e higados fueron colonizados con una cepa virulenta de S. aureus despu6s de su administraci6n experimental por aerosol. Las traqueas, higados y articulaciones tibio-tarsianas de algunos pavos adultos sanos fueron colonizados en forma natural con S. aureus y varias especies de estafilococos coagulasa negativos. Staphylococcosis in turkeys has been recognized for many years, and several studies on its pathogenesis have been reported (10,11,14). The clinical disease is associated with systemic spread of Staphylococcus aureus and multiplication in the liver, spleen, and other internal organs. Localization occurs in the joints and tendon sheaths, resulting in inflammation (synovitis) and lameness and hence reluctance of the turkey to move. Osteomyelitis is usually present; lesions are almost always found in the area of the cartilage growth plate (11). Usually the clinical disease is seen in turkeys between 9 and 20 weeks of age, and frequently it occurs following stress caused by such conditions as other diseases or adverse weather in the case of range turkeys. Staphylococcal synovitis has routinely caused mortality rates of about 5 to 6% in range turkeys raised in