An observational analysis of selected Nightline program transcripts was undertaken to advance understanding of conversational arguments used in the service of public policy debate. Results indicate that Nightline discussions involved more compound structural variations, but fewer simple, convergent and eroded argument structures than had been found in previous research. In contrast to previous efforts, the development of prompter and delimitor argument structures was also identified. In addition, the program's moderator, Ted Koppel, used challenge structures as his primary method of proposing (...) issues for debate. Discussion focuses on features of Nightline argument complexity and proposes directions for future research. (shrink)