Respiratory syncytial virus (RSV) is prone to generating the copy-back type of defective viral genomes (cbDVGs). cbDVGs play crucial roles in RSV pathogenesis by modulating innate immunity and directly interfering with infectious virus replication. Clinically, the timing of cbDVG emergence impacts the severity of RSV infection. DVGs are also considered a novel therapeutic approach for combating viral infections. Therefore, detecting DVGs and comprehensively understanding their functions during RSV infection are paramount. To facilitate these studies, in this chapter, we provide a summary of the commonly used methods for the detection, purification, and production of RSV cbDVGs.