This paper is devoted to the analysis of an experimental bladed disk with contact and friction in the blade roots. The impact of this non linearity on the forced response of the assembly is numerically investigated using a multiharmonic balance method. The full-size finite element model is reduced using a component modes synthesis method and taking centrifugal stiffening into account so as to obtain reduced models of the disk and of the blades. The blade frequency mistuning is measured and introduced in the model. With Coulomb's law of friction, a sensitivity analysis is performed in which the influences of the excitation level and of the rotational speed are studied. The numerical results are compared with the experimental results.