COST – European COoperation in the field of Scientific and Technical Research – is the oldest and widest intergovernmental European network for cooperation in research. COST Action 725 (running from 2004 to 2009) aimed at and succeeded in establishing a European data base of phenological observations, classifying the data according to one common system and using the data in scientific peer reviewed papers. COST725 organized many workshops and conferences that helped to bring together not only the European, but also the global, phenological community. One of the highlights of COST725 was the boxed entry "Phenological responses to climate in Europe: the COST725 project" in the AR4 of IPCC in 2007. And last, but not least, although the action ended in April 2009 a follow up will be launched in 2010 under EUMETNET/ECSN