Abstract: A pneumatically operated press, particularly for pressing grapes, has a cylindrical drum which is rotatable about a horizontal axis.An internal membrane separates the drum into a pressing space in which the groups are pressed and an air space to which compressed air is introduced.A side wall of the drum defining the pressing space is perforated for passing the juice from the space and an opening in this side wall admits the grapes before and after pressing.The drum is cylindrical with the perforated side wall comprising half the drum surface and presenting a smooth surface to the membrane.The membrane is connected to the drum at opposite sides of its axis by connecting strips.