Method for pressure and temperature control of a fluid, in particular helium, in a series of cryogenic compressors, comprising the steps: - measuring an actual rotational speed for each compressor (V 1, V 2, V 3, V 4), - measuring an actual inlet pressure (p ist) and an actual inlet temperature (T ist) at the inlet of the first compressor (V 1) of the series, arranged furthest upstream, - stipulating an inlet pressure setpoint (p soll) for the first compressor (V 1) of the series, - determining a rotational speed index (D i) for each compressor (V 1, V 2, V 3, v 4) from a maximum rotational speed (n i,max) of the respective compressor and the actual rotational speed (n i) of the respective compressor (V 1, V 2, V 3, V 4), - determining a proportional value (prop) from the deviation of the actual inlet pressure (p ist) from the inlet pressure setpoint (p soll), - determining a priority value, wherein, if the proportional value (prop) is smaller than the smallest rotational speed index (D i) of all the compressors (V 1, V 2, V 3, V 4) of the series, the priority value is determined from the proportional value (prop), and wherein, if the proportional value is greater than the smallest rotational speed index (D i) of all the compressors (V 1, V 2, V 3, V 4) of the series, the priority value is determined from the smallest rotational speed index (D i) of all the compressors (V 1, V 2, V 3, V 4) of the series, in order to base the priority of the control on the control of the inlet temperature at the first compressor, - determining an inlet temperature setpoint (T soll) for the first compressor (V 1) of the series and a rotational speed setpoint (n 1,soll, n 2,soll, n 3,soll, n 4,soll) for each compressor (V 1, V 2, V 3, V 4) with the aid of the priority value, - adjusting the actual inlet temperature (T ist) of the first compressor (V 1) to the determined inlet pressure setpoint (T soll), and - adjusting the actual rotational speed (n i) for each compressor (V 1, V 2, V 3, V 4) to the determined rotational speed setpoint (n 1,soll, n 2,soll, n 3,soll, n 4,soll). - measuring an actual rotational speed for each compressor (V 1, V 2, V 3, V 4), - measuring an actual inlet pressure (p ist) and an actual inlet temperature (T ist) at the inlet of the first compressor (V 1) of the series, arranged furthest upstream, - stipulating an inlet pressure setpoint (p soll) for the first compressor (V 1) of the series, - determining a rotational speed index (D i) for each compressor (V 1, V 2, V 3, v 4) from a maximum rotational speed (n i,max) of the respective compressor and the actual rotational speed (n i) of the respective compressor (V 1, V 2, V 3, V 4), - determining a proportional value (prop) from the deviation of the actual inlet pressure (p ist) from the inlet pressure setpoint (p soll), - determining a priority value, wherein, if the proportional value (prop) is smaller than the smallest rotational speed index (D i) of all the compressors (V 1, V 2, V 3, V 4) of the series, the priority value is determined from the proportional value (prop), and wherein, if the proportional value is greater than the smallest rotational speed index (D i) of all the compressors (V 1, V 2, V 3, V 4) of the series, the priority value is determined from the smallest rotational speed index (D i) of all the compressors (V 1, V 2, V 3, V 4) of the series, in order to base the priority of the control on the control of the inlet temperature at the first compressor, wherein, if the proportional value (prop) is smaller than the smallest rotational speed index (D i) of all the compressors (V 1, V 2, V 3, V 4) of the series, the priority value is determined from the proportional value (prop), and wherein, if the proportional value is greater than the smallest rotational speed index (D i) of all the compressors (V 1, V 2, V 3, V 4) of the series, the priority value is determined from the smallest rotational speed index (D i) of all the compressors (V 1, V 2, V 3, V 4) of the series, in order to base the priority of the control on the control of the inlet temperature at the first compressor, - determining an inlet temperature setpoint (T soll) for the first compressor (V 1) of the series and a rotational speed setpoint (n 1,soll, n 2,soll, n 3,soll, n 4,soll) for each compressor (V 1, V 2, V 3, V 4) with the aid of the priority value, - adjusting the actual inlet temperature (T ist) of the first compressor (V 1) to the determined inlet pressure setpoint (T soll), and - adjusting the actual rotational speed (n i) for each compressor (V 1, V 2, V 3, V 4) to the determined rotational speed setpoint (n 1,soll, n 2,soll, n 3,soll, n 4,soll).