Concern for transmission of microorganisms in dentistry extends beyond hepatitis B virus and HIV-1. The herpesviruses--HSV, VZV, EBV, HCMV, and HHV-6--cause persistent infections in most of the population and are shed in saliva. Seronegative or immunocompromised dental-care providers and patients are at greatest risk of infection although reinfections may occur in immunocompetent patients. Respiratory viral infections are frequently transmitted within the dental office among staff and between staff and patients. Although most of these infections are of little consequence, others may cause lost time from the office or, occasionally, debilitating, sometimes fatal, disease. The prevalence of infection with M. tuberculosis, previously on a downward trend, is increasing in association with the AIDS epidemic. The transmission of tubercle bacilli by way of aerosols exposes dental-care providers to possible risk of infection. Awareness of the diseases that can be caused by these agents, the ubiquitous nature of these agents, and the prevalence of asymptomatic infections serve as further reinforcements of the need to follow recommended infection control guidelines.