Abstract: In controlling the dryer section of a paper machine, the basis weight and moisture of the paper web, the energy fed into the drying cylinders of the dryer section and the machine speed are measured, and then the surface temperature of the drying cylinders is predicted on the basis of the measured values. At the same time, the actual surface temperature of the dryer cylinders is also measured, and if the measured value deviates from the predicted value, any defects in the drying apparatus can be detected quickly. In another aspect, a determination is made of the normal correlation between the power consumption of the drive motors of the cylinders in the drying apparatus and the machine speed. These variables are also measured, and if the correlation of the variables is deviant, it can be concluded that there is a failure in the drying apparatus. In that case it is possible to identify the dryer cylinder where the failure is by measuring the temperature of the cylinders.