A numerical methodology for the prediction of vibratory loads arising in wing-proprotor systems is presented. It is applicable to tiltrotor operating conditions ranging from airplane to helicopter-mode flights. The aeroelastic formulation applied takes into account the aerodynamic interaction effects dominated by the impact between proprotor wake and wing, along with the mutual mechanical influence between elastic wing and proprotor blades. A boundary integral formulation suited for configurations where strong body-vortex interactions occur yields the aerodynamic loads, and beamlike models are used to describe the structural dynamics. A harmonic balance approach is applied to determine the aeroelastic solution. In the numerical investigation, first, the aerodynamic solver is validated by correlation with experimental and numerical results available in the literature, then the vibratory loads transmitted by the wing-proprotor system to the airframe are predicted, focusing the attention on the analysis of the different aerodynamic contributions. Nomenclature f aer = vector of generalized aerodynamic forces f nl str = vector of nonlinear structural contributions G = Green function K b , K w = radius of gyration of blade and wing cross sections L b v , L b w , M b = blade sectional aerodynamic loads L w v , L w w , M w = wing sectional aerodynamic loads M, C, K = mass, damping, and stiffness matrices M x , M y , M z = wing moments from pylon and proprotor m b 0 , m w 0 = blade and wing reference masses per unit length p x , p y , p z = blade section inertial forces q = vector of generalized coordinates q x , q y , q z = blade section inertial moments S p B , S p W = proprotor body and wake surfaces S w B , S w W = wing body and wake surfaces T = blade tension t = time u I = velocity induced by far wake V x , V y , V z = wing forces from pylon and proprotor v = body velocity v b , w b = displacements of blade elastic axis v w , w w = displacements of wing elastic axis x = blade and wing spanwise coordinate x, y = observer and source position x b , x w = blade and wing section degrees of freedom c , s = gimbal degrees of freedom b , w = blade and wing section pitch angle # = time delay b , w = blade and wing torsion rigidity b 1 , b 2 = flap and lead-lag blade bending stiffnesses w 1 , w 2 = flap and chordwise wing bending stiffnesses w = wing mass radius of gyration b , w = blade and wing elastic torsion deflection ' = velocity potential = normal velocity on the body _ = time derivative 0 = space derivative