Sales of high-caffeine energy drinks have increased substantially in the UK in recent years, with such drinks being particularly popular amongst young people. Alongside this, there has developed a trend for combining energy drinks with alcohol, either in the form of premixed alcoholic drinks or by mixing non-alcoholic energy drinks with spirits. Strong concerns have been expressed about the possible dangers to health of consuming large doses of caffeine together with alcohol. This briefing paper summarises the evidence available so far and makes recommendations for action.