The Hog1 MAP Kinase is a master regulator of the adaptative response to hyperosmostic stress in S.cerevisiae. When exposed to high osmolarity, multiple processes are impaired compromising cellular homeostasis. This situation must be restored by triggering an adaptative program that ensures cell survival. Whereas Hog1 effects on the modulation of cell cycle progression, transcription and translation as well as the synthesis and retention of glycerol have been partially deciphered, it is very likely that some of the cellular responses dealing with osmostress remain still unknown. By the use of proteomics, biochemistry and genetics, our main goal is to identify new targets of the Hog1 MAPK in order to widen the understanding of adaptation to stress. Being p38 MAPK the mammalian counterpart of the Hog1 MAPK and given the conservation of the signaling cascade from yeast to humans, this information would be extremely useful for the identification of the human homologs of the yeast new targets as well as the characterization of new adaptative responses in higher eukaryotes.