It is generally agreed that middle ear reconstructive surgery performed with tympano-ossicular homografts produces superior functional results compared with prosthetic material, especially with respect to extrusion rate. The use of homografts, though, has been seriously hampered recently by the fear of transmission of human immunodeficiency virus (HIV) infection. In HIV-infected patients, the virus is primarily found in the cells of the lymphoid and monocytic lineage. The nature of the tissues in the eardrum and ossicles, mostly fibrous tissue and compact bone without marrow, suggests that little virus load should be found in homografts. Indeed, culturing minced homograft tissue from two HIV-infected donors with acquired immune deficiency syndrome (AIDS) in a sensitive culture system with PHA-stimulated lymphoblasts produced no virus. Before use, homografts undergo a fixation procedure in 5% formaldehyde and then are kept in a solution containing Cialit as a preservative. The authors therefore examined the capacity of formaldehyde and Cialit to reduce the infectivity of HIV in models of infected tissue as measured in vitro. The reduction of in vitro infectivity due to these treatments was at least 10(5)-fold and 10(2)-fold, respectively. Coupled with the low virus burden in tympano-ossicular tissue, our data suggests that the fixation procedure affords such a reduction in infectivity that the risk of HIV transmission, even from an HIV-infected donor, is vanishingly low.