Abstract. The dynamics of quantum fields in de Sitter space is radically different from the flat space case. For light scalar fields, perturbation theory is plagued by infrared divergences which require resummation techniques. Existing such techniques, developed for flat space quantum field theory (QFT) are difficult to implement in curved spaces mainly because of the phenomenon of gravitational redshift. I present recent work on this topics concerning a new formulation of QFT in de Sitter space which exploits as much as possible de Sitter symmetries and the power of a momentum representation. This p-representation solves the gravitational redshift problem and allows one to formulate standard resummation techniques of QFT in an efficient way. I discuss recent applications concerning the calculation of field correlators and the issue of spontaneous symmetry breaking in de Sitter space.