AbstractPublished information on the basic lead azide series is discussed with particular reference to the gamma modification of basic lead azide I. A sample of this product has been prepared and the absence of significant impurity confirmed by X‐ray diffraction analysis. Infrared absorption analysis has indicated the presence of PbO bonding and the absence of HO bonding. The product is therefore an oxyazide containing neither hydroxide nor water of crystallisation. Chemical analysis confirms that the Pb(N3)2:PbO ratio is less than one.