One advantage of using 9-1-1 CFS records to identify potential instances of terrorist surveillance is that callers have deemed an individual’s behavior sufficiently suspicious to motivate them to make the 9-1-1 call. A second advantage is that 9-1-1 call data are public information that can be analyzed without infringing on individuals’ privacy rights. The article emphasizes that 9-1-1 CFS data should not be analyzed in isolation for homeland security purposes. Rather, analyses should be used to augment a jurisdiction’s ongoing counterterrorism efforts by providing an additional information source that can assist in identifying locations or types of locations at an elevated risk for attack. This information can be cross-referenced with other investigative information, including known threats to specific locations or types of infrastructure. In some cases, information can also be extracted for use in followup investigations, such as vehicle tag numbers related to certain suspicious activity. The method presented for analyzing 9-1-1 calls has four major phases: the preprocessing of the 9-1-1 CFS data in order to produce a single searchable dataset; filtering the dataset by type and keyword in order to identify incidents that might constitute surveillance or probing activity and reviewing the remaining incidents for relevance; identifying the clustering of incidents by location, time, and type of activity; and prioritizing clusters of incidents and searching for additional information to test whether the cluster locations are at risk of being targets. 1 table, 1 figure, and 4 notes