[en] The Generation IV reactors all have the potential to play a significant role in future scenarios dealing with transmutation of spent fuel from LWR power reactors. The nature of the flux spectrum, thermal or fast, is the major factor in the effectiveness of transmuting various transuranic isotopes. We conclude that each Generation IV reactor concept could have a role, if properly co-ordinated and supported by significant development programmes. The fast reactor concepts (liquid metal and gas-cooled) are the most effective in consumption by fission of unwanted actinides (plutonium, neptunium, americium and possibly curium). Thermal spectrum concepts (water-cooled reactors with and without inert-matrix cores, high-temperature gas-cooled reactors with and without inert-matrix cores, and liquid-salt-cooled thermal reactors) all can potentially reduce some of the minor actinides, even if only used in a single pass. When teamed up with subsequent fast-reactor irradiations to reduce higher minor actinides (specifically americium and curium), their use could result in reducing the number of fast burner reactors required, per spent-fuel-producing LWR, compared to a system of only LWRs and fast burner reactors. After listing the six main Generation IV candidates with attributes, benefits and viability concerns, this presentation will focus on one example of fast spectrum systems and two thermal spectrum systems to indicate transmuting capabilities of both types of systems. These will be used for illustrative purposes only and are not meant to give any indication of the relative importance of these systems to concepts not mentioned. Likewise, the figures and graphs in this paper are presented without alteration from the originators (see acknowledgements), and are for illustration purposes only. (authors)