A capping and de-capping apparatus (100) for capping and de-capping tubes (112) disposed in a tube holding rack (111) having a two-dimensional array of apertures (114) for holding the tubes (112). The apparatus (100) comprises a rack support (110) for supporting the tube holding rack (111), a head unit (120) adapted for carrying a cartridge (152) comprising at least one capping and de-capping gripper (122), a drive system (130) for moving the rack support (110) and the head unit (120) relatively towards and away from one another, in order to cause engagement or disengagement of the capping and de-capping gripper (122) with or from a cap (113) of at least one tube (112), and a drive system (140) for rotating the capping and de-capping gripper (122), wherein rotation in one direction causes attachment of the cap (113) to the tube (112) and rotation in the opposite direction causes detachment of the cap (113) from said tube (112).