An improved electrochemical polymer electrolyte membrane cell stack is provided that includes one or more individual fuel cell cassettes, each fuel cell cassette having at least one membrane electrode assembly, fuel flow field and oxidant flow field. Within each fuel cell cassette, each membrane electrode assembly has at least one manifold opening for the passage of reactant manifolds through the cassette, all of which are bonded about the perimeter by a sealant, and each flow field has at least one manifold opening and any manifold openings on the flow fields which do not correspond to a manifold providing reactant for distribution to such flow field is bonded about its perimeter by a sealant. Each fuel cell cassette may also contain other typical components of a electrochemical polymer electrolyte membrane cell stack, such as separator plates or coolant flow fields, which also have manifold openings which may or may not be bonded about the perimeter. The membrane electrode assembly, flow fields, and other components are encapsulated along the peripheral edges by a resin such that the entire periphery of the fuel cell cassette is encapsulated by the resin.