Thermal expansion of the wurtzite phase of ZnS was measured using a back‐reflection Debye‐Scherrer x‐ray camera. Experimental results indicate that retrograde behavior is exhibited both perpendicular and parallel to thecaxis at 60°±5°K. The molar volume decreases approximately 0.30% from 300° to 60°K and then increases slightly upon further cooling. Lattice parameters obtained at 25°C area0=3.8226±0.0003 Å andc0=6.2605±0.0015 Å.