This chapter discusses the characteristics of the insanity defence in the Dutch criminal justice system. In the Netherlands, a state with a moderately inquisitorial system, insanity evaluations can be ordered by the prosecution or by the court. In only a small minority of cases is the defence raised by the defendant. A first characteristic of the Dutch insanity defence is that there is no legal criterion specifying the conditions under which the presence of a mental illness substantiates an insanity plea. This is different from other legal systems, where the criteria for insanity are usually specified—an example is the M’Naghten Rule in Anglo-American jurisdictions. A second characteristic is that, while many jurisdictions use the dichotomy ‘sane’ versus ‘insane’, in the Netherlands three levels of criminal responsibility are used: responsibility, diminished responsibility, and (complete) insanity. A third characteristic concerns the fact that forensic psychiatrists and psychologists must render an explicit opinion about the defendant's (degree of) criminal responsibility (in the absence of a legal criterion for insanity). These three features of the Dutch system remain a topic of debate. This chapter discusses the Dutch regulations and case law, together with relevant practical problems and scholarly reflections.