Assessment of the risk of impact from most radionuclides is based on the total radiological dose rate to the organism of concern. However, for uranium (U) there can be greater risk from chemical toxicity than radiological toxicity (depending on the isotopic composition). Chemical ecotoxicity of U is dependent on several environmental parameters. The most important are carbonate content, because of the formation of soluble carbonate complexes, and divalent cation content (Ca++ and Mg++), because of their competitive interaction with the uranyl ion (UO2 ++). This study summarizes the literature available to set PNECs (predicted no-effect concentrations) for chemical toxicity of U to non-human biota. The corresponding radiological doses were estimated, and as expected chemical toxicity proved to be the greater concern. There were limited data from some types of biota; however, PNECs for the types of biota of interest were as follows: • terrestrial plants—250mgUkg−1 drysoil; • other soil biota—100mgUkg−1 drysoil; • freshwater plants—0.005mgUL−1 water; • freshwater invertebrates—0.005mgUL−1 water; • freshwater benthos—100mgUkg−1 drysediment; • freshwater fish at water hardnesses of: – <10mgCaCO3 L−1 (very soft water)—0.4mgUL−1 water; – 10–100mgCaCO3 L−1 (soft water)—2.8mgUL−1 water; and – >100mgCaCO3 L−1 (hard water)—23mgUL−1 water; or – as a function of hardness—0.26 (hardness asmgCaCO3 L−1) • mammals—0.1mgUkg−1 bodyweightd−1.