Summary of a ‘Resource Assessment’ and a series of ‘Technology Assessments’ as part of the ‘Tidal Stream Work Package’ component of the Marine Energy Challenge. The methodology behind the approach is explained. The Resource Assessment is undertaken in the form of a literature review of the UK and European tidal stream and marine current resource, as well as other information on the global resource. The resource has been estimated for the UK, Europe and globally, split into different types of site (e.g. high/medium velocity, shallow/deep water). Given the information sources available, it is anticipated that the tidal stream energy resource estimates will be more accurate for the UK and Europe than globally. Technology assessments estimated the capital costs, operation and maintenance costs, and the energy production for two different types of horizontal axis turbine (located in two baseline sites with different water depths).