Tsunamis are relatively rare events and most of their evidence is perishable. Therefore, it is very important that reconnaissance surveys be organized and carried out quickly and thoroughly after each tsunami occurs, to collect detailed data valuable for hazard assessment, model validation, and other aspects of tsunami mitigation. Since the early 1990s, post-tsunami reconnaissance surveys have been organized following each major destructive tsunami to make measurements of runups and inundation limits, to collect associated data from eyewitnesses such as the number of waves, arrival time of waves, and which wave was the largest, and to assess human response to tsunami danger. The surveys have been organized on an ad-hoc basis, facilitated and coordinated by the IOC and ITIC working with the affected country, and conducted by international academic tsunami researchers (International Tsunami Survey Team, ITST). The IOC Post-tsunami survey field guide (Manual and Guides 37, 1998, revised 2012, SC .98/WS/24) has been prepared to guide surveys, identify methods, measurements, and observations to be taken, and to standardize data collections. The Tsunami Bulletin Board e-mail service has been used for quickly organizing ITST surveys and for sharing of the observations from impacted areas.