Treating malnutrition is a medical imperative, yet the world's response is falling desperately short. Dr. Tido von Schoen Angerer, Director of Médecins Sans Frontières’ Access Campaign, looks at our response to another recent medical imperative – the decision, in the face of adversity and sometimes even commonly accepted orthodoxy, to treat patients for HIV/AIDS – and asks whether there is not something that can be learnt. How can we overcome the ambition gap in treating malnutrition?