Abstract: A mop (12) is wrung by means of a mop wringer (10) comprising a housing (50), a pair of rotatable, wringing rollers (68, 70) having resilient roller bodies. At least one of the rollers (70) is movable between an inactive position, in which the rollers (70, 68) are out of contact with one another and in spaced apart relationship, and an active position in which the rollers (68, 70) are in contact with one another and further pressed against the mop (12). The movable roller (70) is moved from its inactive position by the interaction between an L-shaped arm (72), which is caused to swing by means of a handle (90), by means of an arm assembly (96) or by means of a motor (106). The L-shaped arm (72) interacts with a cam surface of a further L-shaped arm (74), on which the movable roller (70) is journalled.