To better understand why perpetrator organizations desist from terrorist violence, we must first understand how perpetrator organizations desist from terrorist violence. Here, I aim to improve our empirical understanding of patterns of collective desistance from terrorism in support of a robust research agenda to advance theory and policy on this topic. I discuss two key challenges for empirical analysis of collective desistance from terrorism: operationalization of perpetrator organizations, and operationalization of collective desistance. To illustrate these challenges, I leverage more than 40 years of event data from the Global Terrorism Database among organizations that carried out terrorist attacks between 1970 and 2013. Using descriptive statistics, I critically evaluate the implications of large-N analyses and illustrate their strengths and limitations.