Purpose: Preventive oncology applies pharmaco-Iogic agents to reverse, retard, or halt progression of neoplastic cells to invasive malignancy, a process that may require administration of agents over long periods of time. Although ototoxicity may be a tolerable side effect of anticancer or antimicrobial therapy, even modest ototoxicity may not be acceptable in agents developed for preventive oncology that are routinely administered to subjects who neither are, nor necessarily will become, clinically ill. Materials and Methods: Age-related shifts in hearing may occur over the course of longterm or openended therapy; consequently, age-adjusted norms enable researchers to better distinguish hearing loss caused by drugs from that caused by aging. Norms for hearing sensitivity are derived from the Baltimore Longitudinal Study of Aging and are the basis for the proposed audiologic monitoring recommendations. Results: Audiologic monitoring recommendations are presented that standardize patient selection, adverse event reporting, posttreatment follow-up, and audiologic testing for potentially ototoxic investigational agents. Conclusion: These recommendations are applicable to trials of investigational agents as well as various classes of drugs used in routine clinical care.