In-use testing of diesel emission control technologies is an integral component of EPA's verification program. Device manufacturers are required to complete in-use testing once 500 units have been sold. Additionally, EPA conducts test programs on randomly selected retrofit devices from installations completed with grants by the National Clean Diesel Campaign. In this test program, EPA identified and recovered a variety of retrofit devices, including diesel particulate filters (DPFs) and diesel oxidation catalysts (DOCs), installed on heavy-duty diesel vehicles (on-highway and nonroad). All of the devices were tested at Southwest Research Institute in San Antonio, Texas. This study's goal was to evaluate the durability, defined here as emissions performance as a function of time, of retrofit technologies aged in real-world applications.A variety of operating and emissions criteria were measured to characterize the overall performance of the retrofit devices on an engine dynamometer. This paper focuses on pollutant removal efficiency, which is calculated from measurements of the engine's baseline emissions as compared to emissions with the emission control device installed. Results show emissions reduction effectiveness in line with those originally verified for the devices. Testing also revealed DOCs and DPFs significantly reduced emissions of gaseous and particle-bound PAHs as well as mobile source air toxics.