A fuel cell assembly comprises a fuel cell stack (200) comprising a plurality of fuel cells, a releasable clamp (235) to retain the components of the fuel cell stack; and a casing (240) into which the stack is insertable. The casing (240) provides means (250, 252) to compress the fuel cell stack components together. Each fuel cell in the stack (200) comprises two electrodes (11, 12) that are mutually spaced so as to form an electrolyte chamber therebetween, and each electrode incorporates a catalyst; the fuel cell stack is made up of plates (202) to define electrolyte chambers and plates (206) to define the gas chambers, the electrodes being sealingly secured between plates in the stack. At least one end plate (230) defines ports (232) to supply or withdraw fluids from the fuel cells.