This review focuses on the ontogeny of factors involved in the transcriptional regulation of Na+,K(+)-ATPase expression. The Na+,K(+)-ATPase enzyme is of vital importance for cell function. It is likely that the limited availability of Na+,K(+)-ATPase in infant tissue is the major limiting factor for adaptation to extra-uterine life in several organs. The factors regulating Na+,K(+)-ATPase gene transcription in infancy are discussed. Special emphasis is given to the role of circulating hormones such as glucocorticoids and thyroxine.