Patients in the industrialized world are at low risk of acquiring nosocomial infections; nevertheless, several aspects of care in the hospital or clinic can place patients at risk from infectious disease transmission. Paramount to the prevention of disease is the strict adherence to universal precautions for all patients. Tuberculosis has again emerged as a potential epidemic capable of dramatic morbidity and mortality. The World Health Organization estimated that 22.6 million people were infected with HIV and that 50 million would be infected by the year 2000. The main types of viral hepatitis are hepatitis A through G. The chance of transmitting hepatitis B virus is higher than the chance of transmitting HIV. As knowledge regarding the pathophysiology and transmission of these diseases has increased in recent years, some insight has also been gained into the problems related to transmission of diseases between individuals. This paper will discuss the transmission of tuberculosis, hepatitis and HIV as related to the dental setting and health-care workers.