On 21 May 1981 the WHO International Code of Marketing Breast Milk Substitutes (hereafter referred to as the Code) was passed by 118 votes to 1, the US casting the sole negative vote. The Code arose out of concern that the dramatic increase in mortality, malnutrition and diarrhoea in very young infants in the developing world was associated with aggressive marketing of formula. The Code prohibited any advertising of baby formula, bottles or teats and gifts to mothers or 'bribery' of health workers. Despite successes, it has been weakened over the years by the seemingly inexhaustible resources of the global pharmaceutical industry. This article reviews the long and tortuous history of the Code through the Convention on the Rights of the Child, the HIV pandemic and the rare instances when substitute feeding is clearly essential. Currently, suboptimal breastfeeding is associated with over a million deaths each year and 10% of the global disease burden in children. All health workers need to recognise inappropriate advertising of formula, to report violations of the Code and to support efforts to promote breastfeeding: the most effective way of preventing child mortality throughout the world.