The medical link between dietary saturated fat, serum cholesterol, and arteriosclerosis redefined meanings for butter in New Zealand, from a celebrated dietary staple to a potentially harmful substance to be closely monitored in the diet. The introduction of a nutritionally endorsed butter substitute, polyunsaturated margarine, heightened this shift. This article addresses the ways in which such links are taken up and negotiated outside the medical sphere. It examines the responses of government, nutritional organizations, the dairy industry, commercial interests, women responsible for feeding coronary heart disease sufferers, and everyday butter consumers. The article concludes that rearticulating meanings for butter along medicalized lines was a highly fraught undertaking, particularly in a country in which dairying was of central economic importance and underpinned national iconography.