This document is part of the outcome of the IAEA's BIOMASS research coordination programme and describes the work carried out during a three year period from 1997 to 2000 by the BIOMASS Fruits Working Group (WG). The document presents the main results such as conceptual advances, quantitative data and models on the transfer of radionuclides to fruit and covers the following particular issues: - a review of experimental, field and modelling information on the transfer of radionuclides to fruit; - the development of a conceptual model for a fruit tree subject to a deposit from atmosphere; - description of an electronic database RADFLUX, which represents a substantial collection (34 fruit crops, from temperate, tropical and subtropical climate) of transfer parameters for use in models of soil–plant–animal systems; - description and results of two model intercomparison studies and a validation study where the models were tested against an independent data set. The document is primarily intended for use by experts in environmental modelling worldwide, operators of the nuclear fuel cycle facilities, Regulatory Bodies of the IAEA Member States.