NOVELTY - An anisotropic polymer electrolyte membrane (PEM) is made by providing a swollen ion conductive membrane having first and second opposing planar surfaces; and hot pressing the swollen membrane to form an anisotropic PEM. At least a first opposing surface of the swollen membrane is contacted with a first perforated member having first and second faces with the first face being in contact with all or part of the first opposing surface of the swollen membrane. The second face of the perforated member is optionally in contact with an absorbent material.    USE - For use in fuel cells i.e. a hydrogen or methanol fuel cell (claimed) useful as power sources for portable electronic devices and electric vehicles.    ADVANTAGE - The PEM has an improved dimensional stability in the XM and YM planes.    DETAILED DESCRIPTION - Manufacture of PEM comprises providing a swollen ion conductive membrane having first and second opposing planar surfaces; and hot pressing the swollen membrane to form an anisotropic PEM. At least a first opposing surface of the swollen membrane is contacted with a first perforated member having first and second faces, with the first face being in contact with all or part of the first opposing surface of the swollen membrane. The second face of the perforated member is optionally in contact with an absorbent material. The anisotropic PM, when made to contact with water and methanol, does not significantly swell in the XM, YM plane of the membrane as compared to the ZM dimension perpendicular to the XM, YM plane.    INDEPENDENT CLAIMS are also included for:    (1) a PEM having a membrane plane defined by dimensions XM and YM and a thickness in the ZM dimension perpendicular to the XM, YM plane, with the PEM having an improved dimensional stability in the XM, YM plane, and comprising an ion conductive polymer having first and second opposing planar surfaces with the surface(s) comprising raised islands of the ion conductive polymer;    (2) a catalyst coated membrane (CCM) comprising the PEM as above, where all or part of the opposing surface(s) comprises a catalyst layer;    (3) a membrane electrode assembly (MEA) comprising the CCM above, where the opposing surface(s) comprises an electrode bonded to the surface;    (4) a fuel cell comprising the MEA above;    (5) an electronic device comprising the fuel cell above;    (6) a power supply comprising the fuel cell above;    (7) an electric motor comprising the fuel cell above;    (8) a vehicle comprising the electric motor above; and    (9) a hot press for treating a PEM comprising perforated planar membrane(s) adapted to be placed in contact with a PEM treated with the hot press.    DESCRIPTION OF DRAWING(S) - The figure shows the hot pressing of a swollen membrane to form a PEM with improved dimensional stability.