The paper considers the near-tip J-integral J tip , the far-field J-integral J far , and the experimental J-integral J exp in a material with sinusoidal variation of the Young's modulus E. The evaluations of J tip and J far are based on the concept of configurational forces; J exp is evaluated from the area below the load point displacement curve, as prescribed by the standard testing procedures. Analytic expressions and/or approximation formulae are derived, how J tip , J far and J exp depend on the system parameters of the material, i.e. wavelength and amplitude of the E-variation and its phase shift with respect to the crack tip position, and the global specimen dimensions. The analyses show that J tip and J far exhibit a strong dependency on the phase shift, but not the experimental J-integral J exp . This is the reason why the current procedures for fracture mechanics testing are not suitable to determine the