Best practice in threat assessment requires the use of standardised, evidence-based tools to assist in case formulation. Considerable numbers of such tools have been developed for use in risk assessment in criminal justice, mental health and community settings: instruments have been published for the threat assessment of cases in specific areas, such as workplace violence, school violence, stalking, and terrorism. However, there has been less attention to a more general and common problem faced regularly by politicians, public companies, those in the talent industry, and others in the public eye. That is how the recipients of problematic or threatening communications can judge which of these need referral to security departments or police for further investigation; and how agencies receiving such referrals can reach initial conclusions as to which cases require prioritisation and which do not. Relevant risks in this area concern not simply violence, the focus of most threat assessment instruments, but also persistence, escalation, disruption of function, reputational damage, financial loss, and psychological harm. The Communications Threat Assessment Protocol (CTAP) is a structured professional judgement tool for the initial threat assessment of unwanted communications, designed to fill this gap. This article details the background to the CTAP and its development into a manualised threat assessment instrument for use both in the private sphere and in policing contexts. It reports the first evaluation of the reliability of the CTAP. The results of this study are promising in terms of the use of CTAP in the initial assessment of problematic communications. (PsycInfo Database Record (c) 2022 APA, all rights reserved)