Background: Glucocorticoid (GC) deficiency is a consequence of various disorders that are by themselves rare. Because of this low prevalence, the low cost of GC replacement therapy and the belief that existing outcomes are good, there has been little interest in development of new and improved pharmaceutical products for treatment of GC deficiency. However, GC replacement therapy is complex: diurnal variation of endogenous cortisol must be replicated, GC needs may change during times of physical and psychological stress and there is no biomarker of its action that can be used to monitor individual dose response. Current Limitations: Recent data suggest that the outcome of established long-term GC replacement therapy may not be as good as previously believed. Short-acting GCs such as hydrocortisone (HC) and cortisone acetate for replacement therapy require 2 to 3 administrations per day. Developing Alternatives: Drug delivery system technologies are now available that could permit design and manufacture of a formulation that could accommodate once-daily administration of HC. Such a formulation would enable more physiological serum cortisol-time profiles than are possible with currently available formulations. This short review provides some background on GC replacement therapy, along with recent data on the outcome of patient groups with GC insufficiency, and briefly discusses some general principles for a controlled-release (‘long-acting’) HC formulation.