Goudier Island is located in the Palmer Archipelago, to the west of the Antarctic Peninsula; it is one of the most frequently visited tourist sites in Antarctica. A number of gentoo penguin (Pygoscelis papua) breeding colonies are located on the island and these have been the focus of one of the longest running experiments to examine the impacts of tourist numbers upon penguin breeding performance anywhere in the Antarctic. In this paper we describe the population trends and breeding productivity (chicks per nest) of the 10 colonies on Goudier Island, all of which have now been monitored for 12 consecutive years beginning in the 1996/1997 breeding season. Our results demonstrate that all colonies show considerable inter-annual variability for both the number of breeding pairs and breeding productivity. Of the six visited colonies, two showed an important and significant statistical decline in the number of breeding pairs. One of these declining colonies is used to determine the breeding chronology dates for all other colonies, an important part of the monitoring procedure used to assess breeding success. Our results suggest that in the future, it would be useful to control for this additional disturbance. Our results further suggest that understanding all of the many subtle influences that impact upon gentoo penguin breeding numbers is complex and that some factors may never be completely identified.