The digital television (DTV) transport stream is designed to accommodate NTSC and DTV caption services. This paper describes how services are inserted into and transported within the bitstream, and the challenges that must be overcome in order to provide correctly formatted and synchronized captioning. Caption service transmission starts at the caption-encoding head-end feeding the DTV encoder (MPEG-II video compression), and ends at the decoding hardware in the DTV receiver. Obstacles to be overcome include ensuring system integration, minimizing codec latency and maintaining synchronization. Awareness of these concerns is imperative for engineers and management in the digital video industry.