A series of Mössbauer, x‐ray, and magnetic measurements has been made on wustite (Fe1-xO). The main new results are: (a) The dependence of the Mössbauer quadrupole splitting on heat treatment is very similar to that of the atomic constant, confirming Hoffman's conclusions on the variation of x. (b) The Zeeman Mössbauer lines of untreated wustite below the Curie temperature are completely smeared out; for a sample treated so as to give minimum quadrupole splitting (minimum x) these lines appear. (c) In a heat‐treated sample a Zeeman splitting in the Mössbauer spectrum is observed well above the bulk wustite Curie temperature. This is interpreted as the imposition by the magnetic decomposition products of a magnetic ordering on the otherwise paramagnetic residual wustite with which they are in intimate contact.