The Optional Protocol to the United Nations (UN) Convention Against Torture and other Cruel, Inhuman or Degrading Treatment or Punishment (OPCAT) is premised on the concept of prevention: that regular examination by independent national and international bodies of those detained and the institutions detaining them will prevent torture, ill-treatment, and cruel, inhuman or degrading treatment occurring. This paper examines how National Preventive Mechanisms (NPMs) in Europe have interpreted the concept of ‘regular’ visits. By July 2018, 38 NPMs had been designated in Europe, the largest number in any region. Drawing upon desk-based research and a survey among these NPMs, this paper illustrates that their practice varies considerably, with diverging views on how ‘regular’ is interpreted; a number of factors coming into play when one is trying to identify what is regular; and the extent to which, even if one could define regularity, any NPM is fulfilling this requirement. It identifies the need for more research, suggests NPMs may wish to examine their own practice and concludes with a call to the UN Subcommittee on the Prevention of Torture (SPT) to provide and expand upon guidance as to the sorts of factors that NPMs may consider when determining when to visit.