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The influence of fiber orientation on the crack propagation behavior wasstudied with single edge-notched specimens which were cut from an injection-moldedplate of short-fiber reinforced plastics (SFRP), at five fiber angles relative to theloading axis, i.e. θ = 0° (MD), 22.5°, 45°, 67.5°, 90° (TD). Macroscopic crackpropagation path was nearly perpendicular to the loading axis for the cases of MD andTD. For the other fiber angles, the crack path was inclined because the crack tended topropagate along inclined fibers. In the relation between crack propagation rate and thestress intensity factor range, ΔK, the propagation rate of fatigue cracks was slowest forMD, and increased with increasing fiber angle. When the crack propagation rate wascorrelated to ΔK/E (Young’s modulus), the relations for different orientations mergedtogether. The crack propagation rate was mainly controlled by ΔK at low rates and bythe maximum stress intensity factor Kmax at high rates. The existence of the core layerhad an influence on the fatigue crack propagation behavior of injection-molded plates.It accelerated crack propagation in MD direction, and decelerated in TD direction.