The invention relates to a device used in parallel microsynthesis. Microcompartments that are open on both sides are disposed in a flat arrangement in a microcompartment matrix (4) and are hermetically closed by pressure exerted on both sides by plungers (6) that are covered by a sealing film (11). A layer, produced from elastic material (9) and disposed between the plunger (6) and the sealing film (11), ensures that a continuous pressure is exerted on all microcompartments of the microcompartment matrix (4) that is loosely retained by a frame structure (1). Elevations (2) that project in both directions vertically to the plane of the microcompartment matrix (4) prevent the deformable thin layer from elastic material (9) from escaping laterally between the plunger (6) and the microcompartment matrix (4) while pressure is exerted. A plurality of microcompartment matrices (4) are simultaneously retained by the frame structure (1) and are hermetically closed by a corresponding number of associated plungers (6) that are fastened on a base plate (7) or a cover plate (8).