The National Animal Disease Center's experience with personnel exposure or infection with pathogenic agents is summarized. A total of 128 laboratory-associated exposures to infectious disease agents were reported. Of these exposures, 103 resulted from known accidents. The other 25 were identified only after the development of clinical or serological manifestations of infection. Thirty-four cases of laboratory-acquired infections were reviewed. Class 3 organisms--Chlamydia sp., Brucella sp. and Mycobacterium sp.--were responsible for 76% of the infections encountered, with Brucella sp. incriminated most frequently. The most commonly reported cause of exposure was associated with hypodermic syringe use. Unknown routes of exposure, presumed to be aerosol related, were the overwhelming explanation involved in the laboratory-associated infections.