The anterior pituitary contains five trophic (hormone-secreting) cell types which are defined by their hormone products. During pituitary organogenesis, these lineages emerge in a stereotypical spatio-temporal pattern from a common ectodermal primordium, Rathke's Pouch (RP), thereby providing an excellent model system to address key developmental processes such as pattern formation, cell specification and differentiation. Genetic studies performed in mice have revealed that secreted factors released from neighbouring tissues are critical for the formation of RP and appear to establish positional identity within RP through regionally-restricted induction of transcription factor gene expression. Together, these transcription factors coordinate progenitor cell proliferation, specification and differentiation via a variety of mechanisms that include the recruitment of cell type specific co-activator and co-repressor complexes. Herein we discuss the roles of key components in the pituitary developmental program with particular focus on functionally conserved genes which are associated with various forms of pituitary hormone deficiency in humans.