The South African Environmental Observation Network (SAEON), which has its origins in the scientific community, has evolved significantly over the last five years. Core government support for this emerging initiative became a reality in 2002, when the first funding commitment was made. The establishment of an ambitious distributed national environmental observation system requires extensive partnership arrangements, ranging from participating government departments, through numerous institutions and the corporate sector, to the active individual researchers. In its first three years, SAEON has established its credentials within the South African scientific community, created and staffed a national office at the National Research Foundation, launched the first three of six envisaged distributed observation nodes, expanded its regional and international relevance, and has made great strides with an educational outreach programme. Three additional nodes are nearing completion and all should be operational by early 2008. The financial and institutional sustainability of SAEON was of paramount importance and consumed most of its energy during this establishment phase. The current three-year period (2006-2008) is devoted primarily to securing the scientific sustainability of the SAEON initiative through its nodes and associated partner networks, and to integrating its various functions.