A method for packing an axial flow chromatography column with a bed of particulate medium of a target bed height, said column comprising: a housing comprising an elongated tubular side wall; opposed, axially spaced first and second end units separated by said side wall, wherein at least one said unit is axially movable by drive means relative to the other said unit; a first filter adjacent to said first unit and a second filter adjacent to said second unit which together with the side wall define an enclosed bed space for containing a bed of particulate medium and wherein relative movement of the first and/or second filter alters the bed height; said first end unit comprising a first valve means for filling of the bed space with said particulate medium; and a first port for adding a liquid to or removing a liquid from the bed space; the second end unit comprising a second port for adding a liquid to or removing a liquid from the bed space; said method comprising the steps of packing said column by means of: i. adjusting the axial spacing between the first and second filters to a distance greater than that of the target bed height; ii. introducing a suspension of the particulate medium into the bed space via the first valve means to provide a bed of particulate medium therein; and iii. compressing said bed of particulate medium to produce the target bed height by axial movement of the first and/or second end filters using said drive means; characterized in that the column and the suspension of particulate medium are pre-sterilized and said packing is carried out under aseptic conditions, in that step iii) is achieved by said drive means which is non-integral to and is external to the column and in that the method further includes the step of: iv)removing or detaching the drive means from said column following said packing steps. a housing comprising an elongated tubular side wall; opposed, axially spaced first and second end units separated by said side wall, wherein at least one said unit is axially movable by drive means relative to the other said unit; a first filter adjacent to said first unit and a second filter adjacent to said second unit which together with the side wall define an enclosed bed space for containing a bed of particulate medium and wherein relative movement of the first and/or second filter alters the bed height; said first end unit comprising a first valve means for filling of the bed space with said particulate medium; and a first port for adding a liquid to or removing a liquid from the bed space; the second end unit comprising a second port for adding a liquid to or removing a liquid from the bed space; said method comprising the steps of packing said column by means of: i. adjusting the axial spacing between the first and second filters to a distance greater than that of the target bed height; ii. introducing a suspension of the particulate medium into the bed space via the first valve means to provide a bed of particulate medium therein; and iii. compressing said bed of particulate medium to produce the target bed height by axial movement of the first and/or second end filters using said drive means; i. adjusting the axial spacing between the first and second filters to a distance greater than that of the target bed height; ii. introducing a suspension of the particulate medium into the bed space via the first valve means to provide a bed of particulate medium therein; and iii. compressing said bed of particulate medium to produce the target bed height by axial movement of the first and/or second end filters using said drive means;