In mammals, the pituitary-derived neuropeptide adrenocorticotropic hormone (ACTH) is a major regulator of adrenocortical steroidogenesis and hormone secretion. However, the mechanism by which adrenal growth is governed by pituitary signals and the role of the pituitary in early adrenal development remain to be investigated. In this work the model organism zebrafish was used to elucidate pituitary adrenal interactions during early vertebrate development. The adrenal homologue in zebrafish is located in the head kidney and termed interrenal organ. The work deals with the analysis of pituitary-interrenal interactions by using pituitary mutants, gene-knockdown embryos and pharmacological interventions. As prerequisite to the main study, zebrafish pomc gene was cloned and characterized and the interrenal organogenesis in wild-type zebrafish was analysed.