During every austral summer since the International Geophysical Year 1957–58 several thousand scientists and support staff have worked in Antarctica. A more recent development is the annual advent of 4000–5000 tourists, who now probably outnumber expedition members in the area covered by the Antarctic Treaty System. Most tourists come by ship, visiting coastal areas of the Antarctic Peninsula and the South Orkney and South Shetland islands that arc readily accessible beween November and March: smaller numbers visit the Ross Dependency and Adelie Land sectors. This article reviews Antarctic Treaty and International Union for the Conservation of Nature and Natural Resources (IUCN) attitudes to tourism, and outlines a preliminary study of shipborne tourism between late December 1991 and March 1992 on Half Moon Island, South Shetland Islands. Within one month (January) a survey team from the Scott Polar Research Institute, University of Cambridge, recorded 14 visits by six tour ships, bringing more than 2000 tourists. In addition, attitudes and expectations of visitors were studied on five ships. Arising from this study, a programme of visitor monitoring is planned as a joint project between British, Chilean, and Argentine scientific institutions during the next five years. Objectives are to find ways of minimizing both short-term and long-term impacts of tourists and other visitors on breeding birds and other ecological communities, and to provide a factual basis for regulation under the Antarctic Treaty System.