Abstract: A flat plate dialyzer and method of making same is disclosed. The method includes the steps of stacking alternate layers of permeable membrane tubing and support material in a curved stacked array, applying a flexible sealing material to the ends of the curved array, cutting off a portion of this sealing material and rotating the curved array toward a flat plane which opens up the permeable tubing to provide a path for blood flow therethrough. Dialysate flows through and around the support material on the outside of the tubing. A casing surrounds the array and contains inlet and outlet ports for blood and dialysate. The sealing material may be applied to the ends of the array in the form of a flange which acts as a compression seal between mating portions of the casing. This method and apparatus results in an improved inexpensive pumpless dialyzer with simple entrance and exit ports for the flow of fluids therethrough.