The high-resolution X-ray diffraction technique was used to determine the entire strain tensor as a function of X-ray penetration depth in a 400 nm W-Ta-W trilayer, which consisted of 150 nm W, 100 nm Ta, and 150 nm W. The strain tensor was calculated in a laboratory reference frame to determine the variation of in-plane strains, epsilon(xx) and epsilon(yy), and the normal strain epsilon(zz), as a function of X-ray penetration depth. Two different methods were then used to determine the strains epsilon(xx), epsilon(yy), and epsilon(zz) in each layer of trilayer. The first approach was based on diffraction peak subtraction, and the second on a linear elastic model. Both indicated that the strain states in the W layers were the same, and that the strains epsilon(xx) and epsilon(yy) in the W and Ta layer were the same magnitude. The difference between the Ta and W arose with the normal strain epsilon(zz), and was due to a Poisson contraction effect. The average residual stresses in the trilayer were determined with the HRXRD data, and also with sin(2) psi and a substrate curvature technique, double-crystal diffraction topography. All three techniques indicated that the average biaxial stress in the trilayer was ca. 1.0 GPa.