A fuel cell powered by direct fuel, for example a direct methanol fuel cell, includes a polymer electrolyte membrane which includes a semi-crystalline polymer. Preferred semi-crystalline polymers include first repeat units comprising sulphonated aromatic group containing moieties linked by --SO.sub.2-- and/or --CO-- and/or -Q-groups, where Q is O or S and second repeat units which include aromatic group containing moieties linked by --CO-- and/or Q groups.