Severe lameness in a large proportion of an Angus cattle herd was attributed to phosphorus deficiency. The diagnosis was supported by a rapid response to phosphorus supplementation of the diet. A brief review of the development and diagnosis of phosphorus deficiency is presented. Practical considerations severely limit the choice of a phosphorus supplement. Directions for the use of the supernatant of high-phosphorus fertiliser and water mixtures, as feed or stock water additive and the production of a phosphorus lick are described. Other phosphorus supplements are discussed with particular reference to the fluorine hazard.