Abstract: A machine for opening bags comprises a pair of spiked rollers mounted adjacent but spaced from each other for rotation in opposite directions. The axes of rotation are parallel and on the same level and a reciprocating knife is disposed between the two rollers. A conveyor brings bags to be opened to the rollers which then carry it onto the knife so that the bag is cut in half allowing the contents to fall out under gravity. The two bag halves may be detached from the rollers by a comb or by making the spikes cyclicly retractable below the roller surface and the mechanism can be enclosed in a pressurized enclosure to restrict the production of dust.