A brief review of the status of arachidonic acid as an essential dietary nutrient for cats is presented. The reproductive performance of male and female cats given a purified diet containing only partially hydrogenated vegetable oil as the fat source from weaning was investigated. Male kittens did not require a supplemental source of arachidonate for normal body weight gain and successful reproduction. Female kittens given the same diet also appeared to grow normally, came into oestrus and conceived, but produced only a limited number of viable litters. Subsequent supplementation of these queens with arachidonic acid did not result in the birth of viable kittens. It is suggested that completion of a normal pregnancy by queens given a diet based on partially hydrogenated oil for protracted periods may require fatty acids in addition to arachidonate.