Safety guidelines for andrology laboratory workers were discussed. The scope of the risk for andrology laboratory workers who handle potentially hazardous pathogens in semen was summarized. It was noted that although acquired immunodeficiency syndrome (AIDS) is a major concern for andrology laboratory workers, its notoriety may distract attention from other potentially hazardous pathogens in semen. Recent studies have shown that 47 to 67 percent of potential or actual semen donors for artificial insemination had signs or histories of sexually transmitted diseases. The types of pathogens present in semen were described. Besides the AIDS virus, hepatitis- B virus (HBV), cytomegalovirus, papillomavirus, and pathogens that cause gonorrhea, chlamydia, mycoplasma, ureaplasma, streptococcus, and trichomonas have been detected in semen. Guidelines for preventing exposure to hazardous pathogens in semen used in the NIOSH andrology laboratory were presented. These include: handling every semen sample as if it were contaminated with sexually transmitted disease pathogens; offering all personnel vaccinations for HBV; avoiding accidental wounds from sharp instruments contaminated with semen; wearing disposable plastic or rubber gloves, a laboratory coat or disposable gown, and safety glasses; disinfecting the outsides of semen collection jars; using disposable laboratory supplies where feasible; placing all used disposables in containers marked for biological hazards and autoclaved; using only mechanical pipetting devices, never by mouth; wearing surgical masks whenever the possibility for aerosolizing semen exists; and no eating, drinking or smoking in the laboratory. Implementing safety precautions for health care and laboratory workers was discussed.