The temperature dependence of the lattice parameters of ZnO was measured by x‐ray powder‐diffraction methods. Retrograde behavior was found to occur perpendicular to thecaxis at 93°K. Lattice parameters at 4.2°K werea0=3.24826±0.00015Å,c0=5.2033±0.0018 Å. These results are compared with those for some other II‐VI compounds.