In a method of operating a combined-cycle plant which is based on a gas-turbine group, the compressor unit of this same gas-turbine group is equipped with an intercooler (9). By detecting parameters which comprise at least the ambient temperature (T), the air humidity (.phi.) of intake air (7) and the outlet pressure (Pic) of the intercooler (9), and by feeding the same to a computer (15), regulation is initiated by the latter, which regulation acts on members (17, 18) in the coolant circuit (13, 13a) between the intercooler (9) and a heat sink (14). The dew-point temperature of the cooled air (10), compressed to an intermediate pressure, downstream of the intercooler (9) is thereby influenced.