What we eat and drink can cause obesity, diabetes, hypertension, and other conditions. In response, many governments have enacted or are considering taxes on unhealthy food and drinks. This report evaluates the rationale behind such taxes; reviews evidence on their effects; analyzes different ways of structuring them; draws lessons from taxes on tobacco, alcohol, and carbon emissions; and offers a framework for assessing their benefits and costs. Taxing can influence what people eat and drink, but it is not a silver bullet. Governments must balance potential health gains against taxes’ limits and costs.