Abstract: Disclosed is a stacking device associated with a bag making machine for producing bags from thermoplastic material. The device includes a stacking station at which successive bags are accumulated in a registered pile. Creation and maintenance of a registered stack is achieved by sequentially operable clamping bars being operationally related such that at least one bar is always in contact with the bag stack as it is being accumulated. On completion of a stack, which is determined by a conventional machine cycle counter, a longitudinally travelling clamp arrangement moves the stack away from the stacking station. The disclosed device is particularly suitable to process high density polyethylene.