RITA (Registry of Industrial Toxicology Animal-data) is a pathology data base for the collection of validated histopathological data on tumours and potentially pre-neoplastic lesions observed in laboratory rodents. To enable a better comparison of information, standardized techniques for the preparation of histological slides have been established for all organs. The current paper describes the guidelines for organ sampling and trimming procedures applied in the RITA project, i.e. the number of sections to be taken, the direction in which an organ should be cut, the localization (anatomical site) from which a sample should be taken, and the size of an organ (or part of an organ) to be placed in cassettes for processing. Schematical illustrations and additional explanations are provided to support the proposed standardized procedures in histology laboratories.