The results of macroscopic magnetization measurements for 2.5° K < T < 900° K and H < 20 kOe , and neutron diffraction studies, on powder and single crystal MnSi are reported. The magnetization measurements are not compatible with zero‐field ferromagnetism below the ordering temperature. An antiferromagnet ⇒ spin‐flop ⇒ saturated paramagnet behavior typical of simple antiferromagnets for T ≦ T N is observed upon increasing H at low temperatures. χ ⊥ is nearly constant in the ordered state, and χ initial = 2χ ⊥ /3 for powdered material. However, in neither powder nor single‐crystal neutron‐diffraction experiments were any additional magnetic reflections observed. Below 30°K certain nuclear reflections consistent with spontaneous zero field ferromagnetism increase in intensity. The depolarization of polarized neutrons transmitted through a polycrystalline sample suggests that MnSi is neither a simple ferromagnet nor a simple antiferromagnet.