The cross-plane and in-plane thermal conductivity of four Si/Si0.7Ge0.3 superlattice structures with periods from 45 Å to 300 Å are experimentally investigated using the 3-ω measurement technique. The experiment is conducted over a temperature range from 70 to 340 K. Results indicate that the cross-plane thermal conductivity decreases with decreasing period thickness (i.e. increasing number of interfaces per unit length). The superlattice with the shortest period exhibits a cross-plane thermal conductivity similar to that of a SiGe alloy. The in-plane thermal conductivity follows a similar decreasing trend with period thickness for the three larger period superlattices, but jumps to higher values for the shortest period superlattice. Additionally, the in-plane conductivity can be 3–4 times higher than the cross-plane value.