This paper discusses the need for, and the value of, a more knowledge-based approach to crime prevention. I will argue the case not by presenting scientific evidence about how we can better prevent crime, but rather by pointing out the many problems caused by the lack of a knowledge-based approach in crime prevention. I will highlight the many pitfalls that, in my opinion, characterise much current crime prevention policy and practise, and discuss how these problems can be rectified by adopting a more knowledge-based approach to crime prevention. I can think of no better topic to address in a festschrift celebrating the life and work of Ken Pease, who during his distinguished career relentlessly has championed a scientific approach to the study and prevention of crime.