Peer review of histopathology findings in safety assessment studies involving rodents and other animals is a relatively recent procedure in toxicologic pathology. It serves to ensure the integrity of the pathology evaluation in safety studies, encourages consistency of diagnostic criteria and use of common terminology, and provides a method of continuing education for participants. The use of a standardized system of pathology nomenclature and diagnostic criteria, such as the Society of Toxicologic Pathologist's Guides for Toxicologic Pathology, is of great value in the procedure. Pathology reviews may involve government-sponsored bioassay programs, in-house industrial corporations, or individual peer reviews suggested or required by government regulatory agencies. Pathology Working Groups can be an integral part of the review process. The extent of the peer review is primarily dependent on the study results; however, other variables such as confidence of the data, study size and duration, complexity, and purpose are also important considerations. Essential components of any peer review, however, include selection of tissues/lesions for review, by a reviewing pathologist, discrepancy resolution, data modification, and documentation of all aspects of the review process. Specific procedures for pathology peer review are discussed. Disagreements among pathologists discovered in peer reviews can be resolved by several methods and examples will be presented. The entire pathology peer review process should be a learning experience for all involved and can help ensure the integrity of animal toxicology studies used for important regulatory decisions involving the use of chemicals in our society.