This document specifies a liquid chromatography tandem mass spectrometry (LC?MS/MS) method for the quantification of the inhibitory substance, nitrofurazone, in milk and milk products. The method has been validated for measuring trace levels of intact nitrofurazone to levels down to 1 ng/g in fluid milk and powdered dairy products on a whole product (i.e. powder) basis. While the method is expected to apply to other dairy matrices, additional validation will be required to demonstrate this.