After a 3rd cycle in Geophysics at Clermont-Ferrand, Bernard Itier joined INRA (now INRAeINRAe) in Versailles in 1973. He first carried out research in micrometeorology. These have been applied to the determination of plant evapotranspiration, the characterization of the oasis effect and the study of spring frost. Director of the Bioclimatology laboratory of Grignon (1985-1988), he was interested in the coupling of physical and physiological criteria for the conduct of irrigation. He then headed the Bioclimatology department (1992-1997) and was then the first head of the "Environment and Agronomy" department at INRAe (1998-2001). At the STUE department of the Ministry of Research (2002-2003) he contributed to the establishment of the Observatoires de Recherche en Environnement (O.R.E.). President of the INRAe Center in Montpellier (2003-2007), he led the collective expertise “Drought and agriculture” (2005-2006). Before retiring in 2012, he invested in the use of agri-environmental models to study the impact of climate change on the water comfort of plants and the availability of water resources ("CIMATOR" project, 2007-2010).