In a harmonized ESA/NIVR project the performance of membrane gas absorption for the simultaneous removal of carbon dioxide and moisture has been determined experimentally at carbon dioxide and humidity concentration levels representative for spacecraft conditions. Performance data at several experimental conditions have been collected. Removal of moisture can be controlled by the temperature of the absorption liquid. Removal of carbon dioxide is slightly affected by the temperature of the absorption liquid. Based on these measurements a conceptual design for a carbon dioxide and humidity control system for the Crew Transport Vehicle (CTV) is made. For the regeneration step in this design a number of assumptions have been made.The multifunctionality of membrane gas absorption makes it possible to combine a number of functions in one compact system. This advantage is demonstrated by comparing the total mass and volume demands of the present CTV ECLSS system design, respectively 522 kg and 1747 I., with the MGA conceptual design. MGA replaces the Condensing Heat Exchanger, LiOH cartridges, the Water Evaporator Assembly and several water storage tanks. Therefore volume and mass reductions of respectively 28 and 25% can be obtained.