Climate change will harm human health, and successful strategies to mitigate the extent of the change will restrict that harm. But new studies show that appropriate mitigation strategies will themselves have additional and independent effects on health, most of them beneficial. The potential value of these co-benefits has not so far been given sufficient prominence in international negotiations. This executive summary, part of the Lancet Series, puts forward 3 key messages: Measures to restrict our output of greenhouse gases may also result in benefits to public health These co-benefits will offset at least some of the costs of climate change mitigation, and should be taken into account in international negotiations The co-benefits to health arising from action on climate change are not widely appreciated. A greater awareness might sweeten the otherwise bitter taste of some climate change policies