The Group on Earth Observations was established to promote comprehensive, coordinated, and sustained Earth observations. Its mandate is to implement the Global Earth Observation System of Systems (GEOSS) in accord with the GEOSS 10-Year Implementation Plan and Reference Document. During the months over which the GEOSS Implementation Plan was developed, many issues surfaced and were addressed. This article discusses several of the more interesting or challenging of those issues-e.g. fitting in with existing organizations and securing stable funding - some of which have yet to be resolved fully as of this writing. Despite the relatively short period over which the Implementation Plan had to be developed, there is a good chance that the work undertaken will be influential for decades to come. ?? 2005 Elsevier Ltd. All rights reserved.