The paper describes the promising possibility to capture CO2 in natural gas fired power cycles through the use of a high-temperature membrane reactor of the methane-steam reforming type with an integrated H-2-separating membrane. Two types of membranes are investigated: Pd membranes, which could allow for zero-emission power cycles, and microporous membranes, the use of which in the present work means that 20% of the generated CO2 is emitted to the atmosphere. The membrane reactor is a complex component and much further work is required to find optimum power cycle operating conditions. Combined cycles with an integrated membrane reactor were investigated and the thermal efficiency in some of these non-optimized cases was superior at 47%. (C) 2004 Published by Elsevier Ltd.