Humans are outstanding in their ability to cooperate with unrelated individuals, and punishment – paying a cost to harm others – is thought to be a key supporting mechanism. According to this view, cooperators punish defectors, who respond by behaving more cooperatively in future interactions. However, evidence from laboratory and real-world settings casts serious doubts on the assumption that the sole function of punishment is to convert cheating individuals into cooperators. In this talk, I will discuss empirical work that has explored the motives underpinning punishment decisions, highlighting the important contributions of inequity aversion and other competitive motives in prompting punishment decisions. I will also talk about the consequences of punishment, both in terms of the targets’ responses and how punishers are viewed by others based on their investments. I will end by discussing how punishment in the lab differs from punishment we observe in the real world, focussing on gossip and centralised punishment institutions. I end by highlighting the need to to consider both legitimacy and rehabilitation if punishers are to safely wield an effective, yet potentially explosive, cooperation-enforcing tool.