Background: Based on a systematic evaluation of experimental animal data, the IARC Monographs provide a critical assessment of carcinogenicity in non-human models, which forms a key component of the overall cancer hazard identification process. Evidence from well-conducted bioassays in rodents and other species allows the identification of agents capable of inducing tumours under controlled conditions and contributes to understanding of potential human cancer hazards.

Objectives and Methods: This presentation aims to describe the process by which evidence from experimental animal studies is identified, reviewed, and synthesized within the IARC Monographs programme. It outlines the criteria used to assess study quality and strength of evidence, as well as approaches for interpreting tumour findings across species, sexes, study designs, tumour sites, dose–response patterns, and rare neoplasms. The presentation also discusses how this evidence is integrated with the evidence of cancer in humans and mechanistic information to inform the overall carcinogenicity evaluation. Recently, the Monographs programme has convened an expert consultation panel to discuss the interpretation of results from studies on cancer in experimental animals and their evaluation, and methodological challenges, as well as the use of “supportive data” in preparation for future trends in the evaluation of the evidence of carcinogenicity. This is particularly relevant in light of the 3R (Replacement, Reduction, and Refinement) principle, which aims to reduce the use of animals in scientific research, including cancer studies.

Results: Selected examples from recent Monographs evaluations, among them, 1,1,1-trichloroethane, 2-bromopropane, PFOA, talc, automotive gasoline, and atrazine; and highlights from the consultation panel discussions illustrate how IARC criteria are successfully applied in cancer hazard identification.

Conclusion: Overall, evidence from experimental animals remains central to the IARC Monographs process, providing both early and robust indications of carcinogenic potential, guiding further mechanistic investigations, and informing risk assessment for human health.