Tattooing carries several medical risks, including the transmission of infectious diseases. We review the published literature on the transmission of hepatitis B virus, human immunodeficiency virus, Treponema pallidum, papillomavirus, Mycobacterium tuberculosis, and other organisms by tattooing. Education, through public health measures, should promote the prevention of infectious disease transmission. Particular populations who could benefit from education include prisoners, individuals involved with correctional facilities, youths, military personnel, and health care providers coming in contact with populations at risk for tattoos.