A molding assembly for casting soft contact lenses especially such lenses formed of hydrophobic material. Such a molding assembly comprises a molding cavity defined by the dies of the assembly and an annular gasket or sealing member joining the peripheries thereof. The perimeter of largest diameter of the molding cavity is defined by contact between a sealing ridge which is part of the concave die or the gasket or sealing member and a bearing surface which is part of the other of the concave die or the gasket or sealing member. The annular gasket or sealing member may have an annular skirt adapted to embrace the concave die in the closed position of the assembly. The gasket or sealing member is carried by the convex die and may be integrally formed in one piece with the convex mold.