Fraud in medical research is a broad term that encompasses several different misdemeanors: falsification, fabrication, plagiarism, and deception. The scale of medical research fraud isn’t negligible, either. While reliable estimates are hard to come by - since people are unlikely to implicate themselves - studies suggest that the true rate of fraud among published studies lies somewhere between 0.01% and 0.4%. Chapter 17 discusses why people choose to commit fraud in medical research and how the scientific system can incentivize this type of behaviour. Additionally, the chapter explores how medical fraud ultimately affects the rate and direction of medical progress through mechanisms such as the squandering of resources and a loss of trust. The chapter concludes by discussing how we can dissuade future misconduct in medical research.