The first Session of the Intergovernmental Coordination Group for the Indian Ocean Tsunami Warning and Mitigation System was held in Perth, Australia, from 3–5 August 2005. The Session was attended by 60 participants from 14 countries in the Indian Ocean, 4 other IOC Member States, 7 organizations, and 23 observers. The objectives of the meeting were to: • gain an understanding of the technology deployment plans of the Indian Ocean countries; • discuss related systems including sea level networks, seismic, data and information management, communications and warning centres; and • establish an intersessional process for continuation of this work and to each agreement on the preferred way forward. To achieve these objectives four technical sessions were held, and reports accepted, on the topics of: • Seismic measurement, data collection and exchange; • Sea level data collection and exchange, including deep-sea tsunami detection instruments; • Tsunami hazard identification and characterisation, including modelling, prediction and scenario development; and • The establishment of a system of interoperable operational centres. To achieve the objective of “an intersessional process”, it was agreed that Working Groups would be established on each of these topics, each with Terms of Reference and action items to be addressed before the second session of ICG/IOTWS in Hyderabad, 13–15 December 2005.