Numerous endocrine systems are characterised by pulsatile hormone secretion with periodicities ranging from minutes to hours [1]. Such endocrine rhythms have been described among others for growth hormone, prolactin, gonadotropins, parathyroid hormone and corticosterone. The oscillatory pattern of plasma hormone levels may be physiologically important to reduce down regulation of receptors and, consequently, to enhance hormone action. Intermittent administration of hormones is now widely used in therapeutics since pulsatile administration of growth hormone releasing factor [2] or gonadotropin-releasing hormone [3] appears to be more efficient than continuous delivery.

Though circumstantial evidence for the existence of fluctuations in plasma glucose and insulin levels was published earlier, the current interest in the pulsatility of pancreatic hormones secretion dates from the now classical study of Goodner et al.[4]. Ten years after its publication, we will review the available data on the existence of oscillations in peripheral and, when available, portal levels of insulin and glucagon both in animals and in man. In vitro data on pulsatile insulin and glucagon release will be reviewed, with emphasis on the mechanisms involved and possible relationships with oscillations in B-cell-membrane potential. Comparative effects of pulsatile and continuous insulin and glucagon delivery will then be analysed. Finally, the potential importance of the mode of insulin delivery for the management of diabetes mellitus will be briefly considered.