To introduce and describe the US Border Patrol (USBP) Tucson Sector Border Patrol Search, Trauma and Rescue Unit (BORSTAR) and to analyze whether the frequency of its activities were associated with the amount of total border patrol law enforcement activities in the area. Descriptive and nonparametric analysis was conducted on data that were obtained on total USBP apprehensions of undocumented immigrants and BORSTAR activities for a consecutive 3-year period. From October 2004 to September 2007 over 1 million apprehensions occurred within the Tucson Sector. During this time, a large number of search, rescue, and medical intervention events occurred. However, only a weak association was found between the frequency of apprehensions and BORSTAR activities. The BORSTAR unit of the Tucson Sector commonly encounters harsh conditions and provides search, rescue, and medical interventions to undocumented immigrants. The frequency of BORSTAR activities is not strongly associated with the volume of USBP law enforcement activities.