The aim of the title project was to investigate the maturity of rotor load calculation models and codes by means of which increased loads caused by wind farm operation can be determined. Part of the project concerns the normal production load conditions, calculated by using the so-called Dutch wind handbook. Another part concerns a number of special load conditions, selected at forehand and measured during campaign measurements (event recordings). The results of the simulation of these special load cases, in time and frequency domain, are compared with measurements, which include also rainflow (Markov) matrices of the continuously measured loads. The comparison is performed on the basis of power spectral densities, the azimuthal binned averages, the rainflow cycles and the 1 Hz (fatigue) equivalent value of the different load signals. The calculations were performed by means of PHATAS-2 (rotor code in time domain), TURBU-1 (ibid, but now in frequency domain) and SWIFT (stochastic wind field simulator) computer codes. A conceivable result is that increase in loading for a wind turbine in a wind farm depends on the spacing of the turbine in the farm. 3 appendices, 30 refs.