Querulous paranoia was once of considerable clinical and academic interest in psychiatry. Over the last 40 years, however, it has virtually disappeared from the professional landscape. This decline occurred at the very time that a proliferation of complaint organizations and agencies of accountability were drawing more and more people into asserting their individual rights through the pursuit of claims and grievances. Querulous behaviour, as a result, far from declining, is on the increase, bringing with it suffering for the querulous and disruption to the organizations through which they seek their vision of justice. This article examines querulous behaviour in the vexatious litigant and in abnormally persistent complainants and petitioners. The phenomenological and nosological issues are outlined and the risks of the emergence of threatening and violent behaviour is emphasized. Threats should not be ignored, for a variety of reasons. Approaches to managing querulous behaviour in the courts and the complaint organizations are discussed, together with the utility of individual therapy. Querulous behaviour should once more take its place among the legitimate concerns of mental health professionals. Those caught up in a querulous pursuit of their notion of justice are amenable to management that can ameliorate their suffering and reduce the disruption they create.