A chromatography column (100) is disclosed comprising a housing (10) comprising a tubular side wall (1); opposed, axially spaced end units (2,3) which together with the side wall define an enclosed bed space to contain a bed of particulate medium, at least one of the end units being slidable in axial direction; an axial drive element (5) connected to the slidable end unit, said drive element extending internally in the column bed space; a drive (4) positioned on or beyond the opposite end unit and connected to the drive element.