Transmission can occur through direct contact in the form of percutaneous inoculation or transfer of infective blood, serum, or plasma or through contamination of mucosal surfaces. Transmission also can occur indirectly through contact with environmental surfaces such as test tubes, laboratory benches, or other accessories. Airborne transmission has been hypothesized, but is undocumented. Risk of transmission can be reduced by frequent handwashing, wearing gloves and protective clothing, proper processing and storage of biologic specimens, and appropriate disposal of waste specimens and contaminated materials. Special precautions should be taken with blood-contaminated needles and syringes. Personnel who frequently handle blood should consider use of a vaccine against the virus, but immune prophylaxis should never be considered a substitute for proper safety techniques in the laboratory. Germicides recommended for decontamination include ethylene oxide gas, stabilized hydrogen peroxide, formaldehyde, and hypochlorite. In general, daily laboratory housekeeping procedures are also suitable for laboratories handling blood specimens. Special attention should be given to visibly contaminated areas or items. A mycobacterial germicide is recommended, and cleaning personnel should wear gloves. 1 note and 22 references.