The past 2 years have seen dramatic progress in our understanding of the molecular basis of prolactin gene expression in the pituitary gland. The identification of the pituitary-specific factor Pit-1/GHF-1 has been a major advance, and it leads to new questions, such as the basis for the tissue-specificity of Pit-1/GHF-1 expression itself. It clearly cannot be the only factor involved, as it is found in three pituitary cell types, yet prolactin is expressed in only one of these. It is probable that a network of trans-acting factors, some tissue-specific and some ubiquitous but hormonally activated, interact to determine the overall pattern of expression of the prolactin gene, and the dissection of this system should provide some valuable insights into endocrine gene regulation in general.