A method is provided of monitoring the leak tightness of a plurality of pneumatically or hydraulically actuated actuators of a machine, in particular a plurality of valve actuators of a medical treatment machine, in which pressure is exerted on the actuators in different combinations during operation of the machine. A common pressure drop occurring during a stationary operating phase at the actuators on which pressure is exerted in the respective combination is measured for a plurality of different combinations of actuators on which pressure is exerted. A respective leak tightness value is determined for individual actuators and/or groups of actuators, with the pressure drop measured for those combinations and in which the respective actuator and/or the respective group of actuators on which pressure is exerted being accounted for in the leak tightness value. A machine, in particular a medical treatment machine, is configured to effect the valve actuator monitoring.